This is Turtle.

I know i've been asking too many questions but i'm fixing up a camp on a Lake in
the Swamp to use for fishing and Cook Up's for friends and it has run down a
good bit and needs a little of everything.

i have a water pump system that is feed by a artesian well feeding a big tank.
The water comes out of the ground through a 2" pipe just rammed in the sand
about 12 feet down and then dug out around it about 2 feet on all sides and
poured concrete in the hole around it and makes the water come up the pipe and
go into the tank. You don't have to pump the water out of the ground for it just
flow up and in the tank with nothing but just a pipe. i have timed it and
measured the water flow and it is flowing at a rate of a little over 1 gallon
per minute. Now I had a tank and pump hooked up to a old sheet metal tank to
pump from but the tank just rusted apart and i need a new one. Yes i know the
Tightwad coming out in me. i called about another sheet metal tank or a plastic
tank of 200 to 300 gallons and found they cost about $270.00 to $400.00. This is
just a camp and i don't live there and only use it maybe 1 or 2 day a month and
need just a holding tank to hold water. If we can come up with a plain jane tank
to hold the water I can have my sheet metal man make me a cover. I talk to my
sheet metal man about making me a tank and he said it would run over $200.00 to
make one because the metal had to be atleast a 18 ga. metal used. He could make
it out of 22 ga. but it may fail because of duriablity.

So What could a fellow use as a tank that would cost less than $200.00 to use as
the water tank for nothing but storing water with no pressure or holes in it for
all the pipes can feed from the top and sucxk out of the top with a pipe down to
the bottom of the tank. I have looked at water tank for watering cattle but they
are long and narrow and the 150 gal. would be all that would fit in the pump
shed which measures 85" X 85" and i need 40" on one side to have the pump and
pump pressure tank in that area which i need 40" X 85" to put the pump &
Pressure Tank in. So I have a space of 45" X 85" to fit the holding tank in and
the highth would have to be less than 6 feet 9 inches high.

I have talked to a farm supply store near here [ 40 miles away ] and he was
checking on a prefab tank made for this application but he has not back with me
as to price or do they still make them. Yes I have thought about 6 Plastic oil
55 gal. or chemical drums piped together but it gets too much of a nightmare to
try to put together in the area allowed.

Is there something in this world that would work in the place of a $250.00 sheet
metal tank made to order or am I going to have to bite the bullet and buy a tank
?

TURTLE

In Mexico they have cheaper plastic tanks, but that is Mexico.

"TURTLE" wrote in message
...

This is Turtle.

I know i've been asking too many questions but i'm fixing up a camp on a
Lake in
the Swamp to use for fishing and Cook Up's for friends and it has run down
a
good bit and needs a little of everything.

i have a water pump system that is feed by a artesian well feeding a big
tank.
The water comes out of the ground through a 2" pipe just rammed in the
sand
about 12 feet down and then dug out around it about 2 feet on all sides
and
poured concrete in the hole around it and makes the water come up the pipe
and
go into the tank. You don't have to pump the water out of the ground for
it just
flow up and in the tank with nothing but just a pipe. i have timed it and
measured the water flow and it is flowing at a rate of a little over 1
gallon
per minute. Now I had a tank and pump hooked up to a old sheet metal tank
to
pump from but the tank just rusted apart and i need a new one. Yes i know
the
Tightwad coming out in me. i called about another sheet metal tank or a
plastic
tank of 200 to 300 gallons and found they cost about $270.00 to $400.00.
This is
just a camp and i don't live there and only use it maybe 1 or 2 day a
month and
need just a holding tank to hold water. If we can come up with a plain
jane tank
to hold the water I can have my sheet metal man make me a cover. I talk to
my
sheet metal man about making me a tank and he said it would run over
$200.00 to
make one because the metal had to be atleast a 18 ga. metal used. He could
make
it out of 22 ga. but it may fail because of duriablity.

So What could a fellow use as a tank that would cost less than $200.00 to
use as
the water tank for nothing but storing water with no pressure or holes in
it for
all the pipes can feed from the top and sucxk out of the top with a pipe
down to
the bottom of the tank. I have looked at water tank for watering cattle
but they
are long and narrow and the 150 gal. would be all that would fit in the
pump
shed which measures 85" X 85" and i need 40" on one side to have the pump
and
pump pressure tank in that area which i need 40" X 85" to put the pump &
Pressure Tank in. So I have a space of 45" X 85" to fit the holding tank
in and
the highth would have to be less than 6 feet 9 inches high.

I have talked to a farm supply store near here [ 40 miles away ] and he
was
checking on a prefab tank made for this application but he has not back
with me
as to price or do they still make them. Yes I have thought about 6 Plastic
oil
55 gal. or chemical drums piped together but it gets too much of a
nightmare to
try to put together in the area allowed.

Is there something in this world that would work in the place of a $250.00
sheet
metal tank made to order or am I going to have to bite the bullet and buy
a tank
?

TURTLE




Hi Turtle,

I might just line a plywood box with some plastic sheeting, maybe the vinyl
like they use for above ground swimming pools....

--

SVL

Around here you could probably find one or two old free fiberglass boats.
Cut it half and/or into some panels.
Glass it together with some wood or steel for strength. Last forever

"PrecisionMachinisT" wrote in message
...

"TURTLE" wrote in message
...

This is Turtle.

I know i've been asking too many questions but i'm fixing up a camp on a
Lake in
the Swamp to use for fishing and Cook Up's for friends and it has run
down
a
good bit and needs a little of everything.

i have a water pump system that is feed by a artesian well feeding a big
tank.
The water comes out of the ground through a 2" pipe just rammed in the
sand
about 12 feet down and then dug out around it about 2 feet on all sides
and
poured concrete in the hole around it and makes the water come up the
pipe
and
go into the tank. You don't have to pump the water out of the ground for
it just
flow up and in the tank with nothing but just a pipe. i have timed it
and
measured the water flow and it is flowing at a rate of a little over 1
gallon
per minute. Now I had a tank and pump hooked up to a old sheet metal
tank
to
pump from but the tank just rusted apart and i need a new one. Yes i
know
the
Tightwad coming out in me. i called about another sheet metal tank or a
plastic
tank of 200 to 300 gallons and found they cost about $270.00 to $400.00.
This is
just a camp and i don't live there and only use it maybe 1 or 2 day a
month and
need just a holding tank to hold water. If we can come up with a plain
jane tank
to hold the water I can have my sheet metal man make me a cover. I talk
to
my
sheet metal man about making me a tank and he said it would run over
$200.00 to
make one because the metal had to be atleast a 18 ga. metal used. He
could
make
it out of 22 ga. but it may fail because of duriablity.

So What could a fellow use as a tank that would cost less than $200.00
to
use as
the water tank for nothing but storing water with no pressure or holes
in
it for
all the pipes can feed from the top and sucxk out of the top with a pipe
down to
the bottom of the tank. I have looked at water tank for watering cattle
but they
are long and narrow and the 150 gal. would be all that would fit in the
pump
shed which measures 85" X 85" and i need 40" on one side to have the
pump
and
pump pressure tank in that area which i need 40" X 85" to put the pump &
Pressure Tank in. So I have a space of 45" X 85" to fit the holding tank
in and
the highth would have to be less than 6 feet 9 inches high.

I have talked to a farm supply store near here [ 40 miles away ] and he
was
checking on a prefab tank made for this application but he has not back
with me
as to price or do they still make them. Yes I have thought about 6
Plastic
oil
55 gal. or chemical drums piped together but it gets too much of a
nightmare to
try to put together in the area allowed.

Is there something in this world that would work in the place of a
$250.00
sheet
metal tank made to order or am I going to have to bite the bullet and
buy
a tank
?

TURTLE




Hi Turtle,

I might just line a plywood box with some plastic sheeting, maybe the
vinyl
like they use for above ground swimming pools....

--

SVL

"TURTLE" wrote in message
...

This is Turtle.

I know i've been asking too many questions but i'm fixing up a camp on a
Lake in
the Swamp to use for fishing and Cook Up's for friends and it has run down
a
good bit and needs a little of everything.

i have a water pump system that is feed by a artesian well feeding a big
tank.
The water comes out of the ground through a 2" pipe just rammed in the
sand
about 12 feet down and then dug out around it about 2 feet on all sides
and
poured concrete in the hole around it and makes the water come up the pipe
and
go into the tank. You don't have to pump the water out of the ground for
it just
flow up and in the tank with nothing but just a pipe. i have timed it and
measured the water flow and it is flowing at a rate of a little over 1
gallon
per minute. Now I had a tank and pump hooked up to a old sheet metal tank
to
pump from but the tank just rusted apart and i need a new one. Yes i know
the
Tightwad coming out in me. i called about another sheet metal tank or a
plastic
tank of 200 to 300 gallons and found they cost about $270.00 to $400.00.
This is
just a camp and i don't live there and only use it maybe 1 or 2 day a
month and
need just a holding tank to hold water. If we can come up with a plain
jane tank
to hold the water I can have my sheet metal man make me a cover. I talk to
my
sheet metal man about making me a tank and he said it would run over
$200.00 to
make one because the metal had to be atleast a 18 ga. metal used. He could
make
it out of 22 ga. but it may fail because of duriablity.

So What could a fellow use as a tank that would cost less than $200.00 to
use as
the water tank for nothing but storing water with no pressure or holes in
it for
all the pipes can feed from the top and sucxk out of the top with a pipe
down to
the bottom of the tank. I have looked at water tank for watering cattle
but they
are long and narrow and the 150 gal. would be all that would fit in the
pump
shed which measures 85" X 85" and i need 40" on one side to have the pump
and
pump pressure tank in that area which i need 40" X 85" to put the pump &
Pressure Tank in. So I have a space of 45" X 85" to fit the holding tank
in and
the highth would have to be less than 6 feet 9 inches high.

I have talked to a farm supply store near here [ 40 miles away ] and he
was
checking on a prefab tank made for this application but he has not back
with me
as to price or do they still make them. Yes I have thought about 6 Plastic
oil
55 gal. or chemical drums piped together but it gets too much of a
nightmare to
try to put together in the area allowed.

Is there something in this world that would work in the place of a $250.00
sheet
metal tank made to order or am I going to have to bite the bullet and buy
a tank
?

TURTLE

You need to rethink the concept of saving 300 gallons. I assume drinking
water in a tank above ground. 30 days of non use could let the little
buggies grow. I grew up on a farm and we used wells for everything. We had
a 40 gallon pressure tank and that was all. Dad said that storage of the
water in the Iowa heat would be a problem. I drained the cattle tanks every
other month for cleaning.

http://www.interstateproducts.com/pillow_tanks.htm

I have used similar stuff for this to water cattle. You would have to build
something to contain it.


http://www.watertanks.com/

good luck

"TURTLE" wrote in message
...

This is Turtle.
(snip) I have talked to a farm supply store near here [ 40 miles away ]
and he was
checking on a prefab tank made for this application but he has not back
with me
as to price or do they still make them. Yes I have thought about 6 Plastic
oil
55 gal. or chemical drums piped together but it gets too much of a
nightmare to
try to put together in the area allowed.

Is there something in this world that would work in the place of a $250.00
sheet
metal tank made to order or am I going to have to bite the bullet and buy
a tank
?
Turtle-
Check with the surplus dealers over around Ft. Polk area. Army sells
stuff like that all the time down there, like the tank off an old water
buffalo or something. No, it won't fit in your pump house, but it is
weather-rated, and probably already carrying a camo paint scheme. (Hey, I've
seen Louisiana swamp camps. Nobody will bat an eye at it.)

Here a current tank they have up for bids, but it was used for diesel
already or something so it won't do you any good. Size and shape is similar
to what I am talking about, though. (If link doesn't drop you in right
place, go uphill or downhill a few clicks to find it.)

http://cgi.govliquidation.com/auctio...&convertTo=USD

aem sends....

"SQLit" wrote in message
news:Jv2Sd.96976$0u.32915@fed1read04...

You need to rethink the concept of saving 300 gallons. I assume drinking
water in a tank above ground. 30 days of non use could let the little
buggies grow.


My thinking here is since the source is artesian, just let the excess water
runoff in to any handy drainage area that will accept it....he is near a
lake...so....

And since the pumping costs are next to nothing, depending on the water temp
he might even be able to Jerry Rig up a couple old car radiators with a fan
and use them to help cool the place....

Government regulations may apply....but then again, it dont seem like Turtle
is very concerned with formalities on this project anyways.

--

SVL

"TURTLE" wrote in message
...


Don't buy a used one but have you checked out those plastic tanks like the
lawn care people use to haul around the stuff they spray? I see all
different sizes most fit in the bed of a small PU truck.

Colbyt

PrecisionMachinisT wrote:

"TURTLE" wrote:

The water comes out of the ground through a 2" pipe just rammed in the sand
about 12 feet down and then dug out around it about 2 feet on all sides and
poured concrete in the hole around it and makes the water come up the pipe
and go into the tank... at a rate of a little over 1 gallon per minute.

That's 1440 gallons a day, all the time? How much do you need to store?

Now I had a tank and pump hooked up to a old sheet metal tank to pump from...

How big was that tank?

...i called about another sheet metal tank or a plastic tank of 200 to 300
gallons and found they cost about $270.00 to $400.00. What could a fellow
use as a tank that would cost less than $200.00...

You might expand the 2' hole around the pipe and line it with EPDM rubber,
with a hose clamp around the pipe and a concrete block compression ring at
the top and a flattish dome covered with welded wire fence and EPDM over that.

...I have a space of 45" X 85" to fit the holding tank in and the highth
would have to be less than 6 feet 9 inches high.

A 3'x7'x4'-tall box would hold 700 gallons, with an 11'x15' folded liner;
3 walls might be reinforced shed walls. The sideways pressure at the bottom
would be about 250 psf. You might screw a flat perimeter 2x4 to the plywood
bottom and sides with and 4 bolted horizontal double 2x4 hoops above that (1
flat 2x4 on the short walls, sandwiched between 2 on the long walls), with
some spiked mending plates to spread the bolt load and 3 single 2x4 hoops
above that, and a vertical 2x4 around the top. I wouldn't go higher than 4'.

I might just line a plywood box with some plastic sheeting, maybe the vinyl
like they use for above ground swimming pools....

EPDM rubber would work, at about 30 cents/ft^2. Two layers of 6 mil greenhouse
polyethylene film might also work, at about 5 cents/ft^2 per layer.

Nick

20 S=3.5^2*3/6'doubled 2x4 modulus (in^3)
30 F=1000'max fiber stress in bending (psi)
40 M=S*F'bending moment (in-lb)
50 W=8*M/84'total force on 7' 2x4 (pounds)
60 PPF=W/7'load per linear foot (lb/ft)
70 C=PPF/62.33'quadratic term
80 D1=(4+SQR(4^2-4*C))/2'depth of 1st hoop from bottom (ft)
90 W1=4-D1'height band width supported by 1st hoop (ft)
100 PRINT "1 2",12*D1
110 C=2*C'quadratic term
120 B=W1-2*D1'quadratic term
130 W2=(-B-SQR(B^2-4*C))/2'band width supported by 2nd hoop (ft)
140 D2=D1-W1/2-W2/2'depth of 2nd hoop from bottom (ft)
150 PRINT "2 2",12*D2
160 B=W2-2*D2'quadratic term
170 W3=(-B-SQR(B^2-4*C))/2'band width supported by 3rd hoop (ft)
180 D3=D2-W2/2-W3/2'depth of 3nd hoop from bottom (ft)
190 PRINT "3 2",12*D3
200 B=W3-2*D3'quadratic term
210 W4=(-B-SQR(B^2-4*C))/2'band width supported by 4th hoop (ft)
220 D4=D3-W3/2-W4/2'depth of 4th hoop from bottom (ft)
230 PRINT "4 2",12*D4
240 C=C/2'quadratic term for single 2x4
250 B=W4-2*D4'quadratic term
260 W5=(-B-SQR(B^2-4*C))/2'band width supported by 5th hoop (ft)
270 D5=D4-W4/2-W5/2'depth of 5th hoop from bottom (ft)
280 PRINT "5 1",12*D5
290 B=W5-2*D5'quadratic term
300 W6=(-B-SQR(B^2-4*C))/2'band width supported by 6th hoop (ft)
310 D6=D5-W5/2-W6/2'depth of 6th hoop from bottom (ft)
320 PRINT "6 1",12*D6
330 PRINT "7 1",12*(D6-W6/2)/2

Hoop #2x4 depth (in)

1 2 43.58255
2 2 38.89918
3 2 33.55583
4 2 27.14029
5 1 21.33781
6 1 16.09097
7 1 6.549896

That's 13 8' 2x4s for the long walls plus 9 4' 2x4s for the short walls...

A 3'x7'x4'-tall box would hold 700 gallons, with an 11'x15' folded liner;
3 walls might be reinforced shed walls. The sideways pressure at the bottom
would be about 250 psf. You might screw a flat perimeter 2x4 to the plywood
bottom and sides with and 4 bolted horizontal double 2x4 hoops above that (1
flat 2x4 on the short walls, sandwiched between 2 on the long walls), with
some spiked mending plates to spread the bolt load and 3 single 2x4 hoops
above that, and a vertical 2x4 around the top. I wouldn't go higher than 4'.

That version would use 4 sheets of plywood and 35 8' 2x4s, about $143 with
the double poly film liner. Welded wire fence on the bottom with a 2x4 hoop
inside the box at the top and bottom and 26 4' vertical studs on 1' centers
would lower the materials cost to $102 and reduce the labor required.

A wall might look like this, viewed in a fixed font, with a few wires across
the top to hold it together:

---
| |screw eye + wire--- - - -
| | film
| |pp - p
| |ol|2|o |
|2x4|ly|x|l
| |yw|4|y
| | ofilm |
| | op
| | do
| | pl |
| | ly
| | yf
| |
... 4'

| | wi
| | ol
| | om |
| | dp
| | po
| | llyfi |
|2x4| y - l
| | w|2|m
| |wo|x|p |
| |io 4|o
| |rd - lyfilm...
--- efencewirefence... - - -

A tank like this could be much larger, with little increase in materials cost.

Nick

http://www.tank-depot.com/product.aspx?id=123

by the time you buy & build a wooden one & line it with plastic plus
the hassle with fittings (if you penetrate the wall) you'll be money &
headache ahead to just buy one

I'd go with plastic. I'd also take another lookat the used plastic 55
gal food grade drums

cheers
Bob

Jonathan Mau wrote:

I have been giving consideration to a big water thermal store also. The
55 gallon plastic drums can be had for CAN$10. What I don't know is the
temperature characteristics. I think these are HDPE. The tanks I have
found in HDPE are only rated at 120 degrees F with a liquid of S.G. 1.7 I
think. I wonder if one could get a few more degrees with a S.G 1 liquid?

Sure. Then again, maybe that rating only applies for rail or truck transport.

I suspect this is an issue of wall thickness, temperature, and pressure
and not an absolute limit of the material.

You might wrap a drum with chicken wire.

My calculations show so far that the lower cost of 55 gallon drums outweighs
the higher cost of insulation as compared to one large tank only considering
the cost of tank(s) and insulation. Throw in all the bits and pieces to run
piping into say between 4 and 18 55 gallon drum tanks and things might change.

You might arrange plastic drums in a square or hex grid and connect them with
short threaded nipples through adjacent holes in the walls near the bottoms
or bulkhead fittings with barb or garden hose adapters. If the drums are
cylindrical, a single PVC bulkhead fitting might connect two of them.

Low-pressure ag applications use "push plumbing"--drill a smooth hole
in a drum with a step bit, and push some smooth tubing into the hole.

Nick

wrote:

I've been looking at this problem as well. My current best plan is to
fill an insulated, EPDM-lined hole in the ground with drain rock, then
cover that with EPDM and insulation and bury the thing under my patio.

Burying could be bad, maintenance-wise. Indoor heat loss might be nicer.

The point of the drain rock is that it's cheap, available and manageable
in bulk, and takes vertical stresses without any engineered structure.

One might say the same about water :-)

In case it's not clear, this is a water tank, not a rock tank .

That's not clear :-)

The rocks fill about 2/3 of the volume of the store, and store a little
less heat per unit volume than water. So the overall tank has to be
upsized a little.

A little? :-)

density Cm Cv
kg/m^3 kJ/kg-C kJ/m^3-C

granite 2640 0.82 2165
limestone 2500 0.90 2250
marble 2600 0.80 2080
sandstone 2230 0.71 1583
water 998.2 4.186 4178

I'm thinking of using "blueboard" extruded polystyrene insulation,
probably the 30 psi variety...

You might get the hole foamed, or forget insulation, if it's large enough.
And float foamboard under EPDM or build a shallow dome for a cover.

Even including the geotextile felt between the EPDM and the drain rock,
this is about $0.30/gallon, and has no size restriction, shape issue,
or safety problem with overheating.

US Patent No. 3,933,628 "Method and Apparatus for the Anaerobic Digestion
of Decomposable Organic Materials," issued to inventor Frederick T. Varani
of Golden, CO on Jan 20, 1976, assigned to Bio-Gas of Colorado describes
a methane generator for a 100,000-cow feedlot, using 2 EPDM-rubber-lined
trenches, each 700' long x 80' wide x 40' deep. They cost $0.02/gallon,
including self-inflated solar covers and excavation.

I do have some reservations about the idea though:

- Maintenance will be a bitch. The tank I'm planning is large (125
cubic yards).

Wow. Why so big? You could put a hundred tons of water in that 15' cube.

Digging 200 tons of wet drain rock out to get to a leak would be very bad.

Very bad.

I'm wondering what I do to make sure there are never any leaks.

Omitting the rocks might help.

- The top of the (unpressurized) tank to the bottom of the rooftop solar
panels will be 23 feet. I'd like to have a drainback system, but then:
- I am pumping up a 23 foot head, and that'll cost $$ for electricity...

You might put a few coils of PT Industries (800) 44 ENDOT PBJ10041010001
1"x300'100psi NSF-certified pipe on the bottom... $59.99 from True Value
hardware stores. Each coil would have 78.5 ft^2 of surface and might have
78.5x30 = 2356 Btu/h-F of thermal conductance, enough to collect 23,560
Btu/h of heat from about 236 ft^2 of solar collectors with a 10 F temp diff.

Nick

I called True Value Hardware. They couldn't find this PBJ10041010001
plastic tubing/pipe. The plastic tubing they did have was over a buck
a foot, more expensive than the 3/4" copper tubing that a local
plumbing supply place could source. Home Depot and Lowe's wanted
similar 1$/foot for PEX tubing.

Nick, have you ever done a test, or do you know of tests, which found a
heat conductance value for copper tubing?

I'm still calling around for reasonable quotes on a shotcrete cistern.
One question is how to do the top for such a cistern. If I put it
under the patio, I can arrange to have a lightweight wooden deck over
it, which could be supported by steel beams. I was thinking I could
glue the blueboard to the underside of the steel, then glue the EPDM to
the underside of the blueboard, but glue + high temperatures makes me
see delamination in the future. There is also the issue of making sure
that rain and whatnot drains off around the cistern and doesn't pool on
top of it.

wrote:

I called True Value Hardware. They couldn't find this PBJ10041010001
plastic tubing/pipe.

TVH has changed their distribution system. My local store says this Endopoly
pipe is only stocked in one of their California warehouses :-) PT Industries
(1 800 44 ENDOT) and others also make cheaper irrigation pipe, eg $54.60
1/2"x400' and $71.60 3/4"x400' 100 psi pipes. US Plastics sells Cresline
3/4"x100' 100 psi pipe (item 24302) for $14.80, less 15% for 12 rolls.

Home Depot and Lowe's wanted similar 1$/foot for PEX tubing.

That's different.

...a heat conductance value for copper tubing?

I measured 30 Btu/h-F-ft^2 including still water on both sides. The water
films dominate the total resistance. IIRC, HDPE's thermal conductance is
about 2.6 Btu/h-F for a foot (vs 223 for copper), or 520 for a 0.06 inch
wall thickness, with no allowance for fouling.

I'm still calling around for reasonable quotes on a shotcrete cistern.

US Patent No. 3,933,628 "Method and Apparatus for the Anaerobic Digestion
of Decomposable Organic Materials," issued to inventor Frederick T. Varani
of Golden, CO on Jan 20, 1976, assigned to Bio-Gas of Colorado describes
a methane generator for a 100,000-cow feedlot, using 2 EPDM-rubber-lined
trenches, each 700' long x 80' wide x 40' deep. They cost $0.02/gallon,
including self-inflated solar covers and excavation.

Nick

In article .com,
wrote:
I'm still calling around for reasonable quotes on a shotcrete cistern.
One question is how to do the top for such a cistern. If I put it
under the patio, I can arrange to have a lightweight wooden deck over
it, which could be supported by steel beams. I was thinking I could
glue the blueboard to the underside of the steel, then glue the EPDM to
the underside of the blueboard, but glue + high temperatures makes me
see delamination in the future. There is also the issue of making sure
that rain and whatnot drains off around the cistern and doesn't pool on
top of it.

You do seem (from here) determined to take the most complicated
approach. To simplify - make your patio from spancrete panels - these
are pre-stressed, pre-cast concrete panels which a crane puts in place.
They are used for ceiling and floor in buildings - getting one to span
your 15 (or less, without rocks) foot hole will be trivial. Or, cast a
top in place, but the spancrete will be easier (no need to form in the
hole). Provide for a slight grade and water will flow off.

Foam will float, so fussing about glue is probably a non-issue. However,
you could glue the foam to the underside of the concrete if you like.
Better yet, use polyurethane spray-on foam, which will glue itself in
place when sprayed. It's also waterproof enough that it's used as
roofing, you you can probably skip the EDPM.

--
Cats, Coffee, Chocolate...vices to live by

Thank you for the pipe info, Nick.

Not to be difficult, but the house is going into a tightly controlled
residential neighborhood. We are removing one tree (out of 70+ on the
lot), and doing maybe 1500 yd^3 of grading, all carefully shaped to
blend with the natural contours of the site. Getting the steeply
angled rooftop solar collectors (flush with roof surface) past the
architectural and site control committee is expected to be a challenge.
Talk of above-ground trenches with self-inflating solar covers is just
not relevant to this problem.

I'd like simplicity, but it has to work within the constraints I have.
I'm also suffering from a lack of information.

Spancrete panels with spray-on foam on the underside sound like just
the thing. Floating isn't relevant, since it has to stay up when I
drain the cistern for maintenance. But strength in compression (the
good thing about blueboard) is irrelevant for the top, and I agree that
spray-on foam sounds like it would stick just fine. I'll look into
these.

Thank you.

Nick, have you ever done a test, or do you know of tests, which found a
heat conductance value for copper tubing?


I have a copy of one test that used a 0.36 inch dia coil of copper
tubing arranged in a vertical helix inside of a 10 inch diameter
cylindrical tank. The coiled tube is about 128 inches long, and the
coil diameter was 8 inches (about 5 turns in the coil).

The water in the cylinder was maintained at a set temperature with an
immersion heater. Cooler water was pumped through the coiled copper
tube. The fluid in the cylindrical tank was not mixed in any way
except natural convection. The U value for the heat exchanger was
calculated using the measured input and output temperatures, and the
mass flows.

The U they got varies with flow rate, but its about 125 BTU/ft^2-hr-F
with a flow rate around 0.7gpm.

Where U is as in the eqn: U = Q/(A (Tb - Tm))
where Tb is bath temp, and Tm is mean temp in tube
A is surf area of tube

I have a pdf file on it, and can email it to you if you like.

This value seems to agree pretty well with the values given he
http://cheresources.com/uexchangers.shtml

Gary

So I'd need 350 feet of 3/4 inch copper tubing to match the thermal
transfer of 1100 feet of Nick's True Value special. To get to 500K
BTU/hour for the pool HX, I'd need 700 feet of tubing, about $800.
That's 70% more $ than the True Value special.

Of course, this tubing would be NSF rated to 500 psi+, and would stop
any oxygen diffusion into the cistern. A similar chunk of 200 feet of
tubing would do the DHW heating, and would look a lot more like what
is normally used for potable water inside Californian houses.

(It looks like getting enough copper tubing to make a size X heat
exchanger, just sitting in a bath of hot water, is just as expensive
as buying a gas pool heater with the same BTU/hr capacity. Wow.)

My architect suggested that, since we'll be shooting several truckloads
of shotcrete to make the retaining walls, the incremental cost of a
shotcrete cistern will probably be small, as it won't take them very
long
to shoot it. So it sounds like that's what we're going to go with,
even
though I don't have any hard numbers on the option.

I called a spancrete manufacturer. The sales guy there said that
servicing a cistern with a spancrete top would require a big crane,
and that he sure wouldn't use spancrete. Why not a wood deck?
:-).

wrote:

So I'd need 350 feet of 3/4 inch copper tubing to match the thermal
transfer of 1100 feet of Nick's True Value special...

No. Please read this carefully, for the third time: the water films
dominate the series thermal resistance. The thin pipe wall material
makes little difference. Ferguson sells 1/2"x400' rolls of 125 psi
ENDOT HDPE pipe for $48, and the outside water film conductance of
1/2" pipe is higher than 3/4" pipe, per square foot.

Nick, again repeating obvious truths to people who will not listen.

wrote:
So I'd need 350 feet of 3/4 inch copper tubing to match the thermal
transfer of 1100 feet of Nick's True Value special. To get to 500K
BTU/hour for the pool HX, I'd need 700 feet of tubing, about $800.
That's 70% more $ than the True Value special.

I think that the biggest part of the difference between U of 30
BTU/hr-ft^2-F that Nick measured, and the value measured in the test
of 125 BTU/hr-ft^2-F is that in Nick's test there was no flow either
inside the tube or outside the tube (except for natural convection).
On the test that I described there was forced flow trough the tube,
which reduces the film coefficient on the inside the tube side.
If I understand your application correctly you will have pumped flow
in the tube, and it seems like a value something like 125 would be in
the ball park for either kind of pipe. Since the pipe is cheap, it
might be good to err on the too much pipe side.

I am working on a prototype of a horizontal pond batch hot water
heater that has a coil of 3/4 inch PE pipe sitting in an insulated and
glazed 6 inch deep bath of sun heated water. I think that the water
bath is going to hit about 120F today, and if so, I will test how good
a job the PE pipe does in extracting heat from the bath. I'll pass on
whatever U value comes out of this.

Gary

Gary,

It sounds like you agree with Nick, that copper pipe is a waste of
money for the pool HX because without pumped (presumably turbulent)
flow on both sides, at least one water film is going to dominate the
series resistance. I certainly agree that once you go with plastic
tubing, it's worthwhile to err on the side of too much pipe. It would
be very nice if the plastic tube HX got a U anywhere near 125
BUT/hr-ft^2-F, it'll warm the hot tub up in a hurry!

I don't have any sense of how big a deal this oxygen diffusion is.
Supposedly the PEX-Al-PEX tubing is better than just PEX specifically
because the Al acts as an oxygen barrier. I guess the dissolved oxygen
is supposed to eat your metal bits over time. If I use PE tubing for
the pool HX, I assume I'll be pumping oxygen into the cistern water.

The oxygen issue seems slightly different that the open vs closed
system issue. Supposedly open systems that expose the water to air
require more maintenance. My assumption is that open systems
accumulate both oxygen but also organics and bacteria and whatnot,
which then all has to be killed and strained from the system to prevent
accumulation in the pipes and so forth.

For the DHW HX, it seems to me that the dominating issue is safety, and
copper tubing seems safer than plastic tubing: Less likely to leak or
crack, less likely to blow out (stronger), less likely to support some
nasty thing growing. Probably more likely to leach poisonous heavy
metals into the stagnating hot water, but that's why we don't make
coffee from the hot water tap.

wrote:

...I don't have any sense of how big a deal this oxygen diffusion is.

Radiant floor people only worry about cast iron pumps.

For the DHW HX, it seems to me that the dominating issue is safety, and
copper tubing seems safer than plastic tubing...

....which loses 12% of its pressure rating for each 10 F rise above 73 F.

ENDOT has a lifetime guarantee that includes labor for the first 25 years.

Nick