I'm in process of replacing my water heater (gas). I've got the new
one out of the carton and it's got all the normal stuff plus something
extra: a bag containing two 3/4" galvanized steel nipples. Each is 2"
long with a blue plastic lining running the length of the inside and
protruding about 1/16" at each end. If I screwed one down on the dip
tube (which seems to be the same color plastic) effectively the water
wouldn't touch the galvanized nipple. I don't know why I'd want this
on the hot side though.

But wait, there's more. At one end of each nipple attached to the blue
plastic lining is a (also) blue plastic ring bringing the outlet
diameter down to 3/8". Inside the ring is a black rubber flap, very
thin, and attached only on one side. Except that it's rubber and
there's a small gap around the black rubber and I can blow the flap
out of the way in either direction, it could be a check valve. There's
no directional arrows on the nipple.

The only reference in the manual is on the repair parts schematic
where these nipples are described as: "Nipple w/Heat Traps". In the
installation section the diagram shows an arrow pointing to the hot
and cold inlets with the description: "3/4" Threaded Nipple". Nothing
about heat traps. The impression is that you could use any 3/4"
nipple.

Does anyone have any idea of the function of these special nipples and
which way they go in. I'm a little worried that the rubber flap is so
flimsy that it'll break off and end up blocking some faucet. Maybe
it's a partially disconnected washer (the hole hasn't been properly
punched out) but why would they reduce the size to 3/8"?

If no one has any good ideas, screw them. I'll just put back the 3/4"
brass nipples I removed from the old heater.

wrote in message
...
I'm in process of replacing my water heater (gas). I've got the new
one out of the carton and it's got all the normal stuff plus something
extra: a bag containing two 3/4" galvanized steel nipples. Each is 2"
long with a blue plastic lining running the length of the inside and
protruding about 1/16" at each end. If I screwed one down on the dip
tube (which seems to be the same color plastic) effectively the water
wouldn't touch the galvanized nipple. I don't know why I'd want this
on the hot side though.

Galvanized pipes rust from the inside out. Good to have both nipples plastic
lined - they last much longer.


But wait, there's more. At one end of each nipple attached to the blue
plastic lining is a (also) blue plastic ring bringing the outlet
diameter down to 3/8". Inside the ring is a black rubber flap, very
thin, and attached only on one side. Except that it's rubber and
there's a small gap around the black rubber and I can blow the flap
out of the way in either direction, it could be a check valve. There's
no directional arrows on the nipple.

The black rubber thing is a heat trap. Keeps the heat inside the heater
when the thing is not being used. A good idea, but this implementation
needs work if you ask me. See below for a better way.



The only reference in the manual is on the repair parts schematic
where these nipples are described as: "Nipple w/Heat Traps". In the
installation section the diagram shows an arrow pointing to the hot
and cold inlets with the description: "3/4" Threaded Nipple". Nothing
about heat traps. The impression is that you could use any 3/4"
nipple.


You can use any 3/4" nipple as long as it's plastic-lined. You just don't
have the heat trapping capabilities with a normal nipple.


Does anyone have any idea of the function of these special nipples and
which way they go in. I'm a little worried that the rubber flap is so
flimsy that it'll break off and end up blocking some faucet. Maybe
it's a partially disconnected washer (the hole hasn't been properly
punched out) but why would they reduce the size to 3/8"?

No, the rubber flap is the heat trap mechanism. I don't think it matters
which way they go in, if it did the mfgr would likely have arrows painted on
them to indicate the direction of flow. However, I think the things are
likely to be completely ineffective in a few years after the rubber flappers
get permanently bent in the outflow (hot-side) or inflow (cold-side)
directions, or they break off. Plus, they don't truly stop all the heat
from getting out.

A better solution is to make a heat trap out of copper pipe. This kind of
trap is nothing more than a loop. Heat rises, but it doesn't sink, so the
heated water will stay in the tank when hot water is not being used and it
won't radiate heat out the first 10 feet or so of pipe coming out of the
tank.

I have such a trap on my tank and the outlet side of the heat trap is as
cold as the incoming cold water pipe if the tank has been sitting for a
while. My loop was 1/2" copper pipe rising 12" out of the heater's hot
side, then across 2", then back down 12" and out to the house. The length
of the up & down sides of the trap do matter, longer is better up to a
point. 6" probably isn't long enough to truly keep the heat in. (If
necessary, the same kind of trap can be applied on the cold water side, but
it probably isn't necessary; the dip tube does the trick there.)

Because this involves laws of physics, it will always work and it will never
have a piece break off and plug up something. Supposedly you can take a long
length of that so-called "flexible" copper pipe and make a loop out of it -
it would do the same thing - but have you ever tried to bend that stuff?

I would go ahead and use them. I agree it sounds questionable as to
how effective they will be long term, as they may tend to stay open
after years of use. On the other hand, there are many great synthetic
materials today that have properties well suited to particular
applications. If the manufacturer chose the right material, they may
in fact work very well.

And while these aren't perfect in stopping all the heat, neither is a
heat trap constructed of pipe. You now have a loop of several feet of
pipe that you have to insulate, and that will still lose heat, plus
some heat does transfer through the water anyway, etc.

wrote:
I'm in process of replacing my water heater (gas). I've got the new
one out of the carton and it's got all the normal stuff plus something
extra: a bag containing two 3/4" galvanized steel nipples. Each is 2"
long with a blue plastic lining running the length of the inside and
protruding about 1/16" at each end. If I screwed one down on the dip
tube (which seems to be the same color plastic) effectively the water
wouldn't touch the galvanized nipple. I don't know why I'd want this
on the hot side though.

But wait, there's more. At one end of each nipple attached to the blue
plastic lining is a (also) blue plastic ring bringing the outlet
diameter down to 3/8". Inside the ring is a black rubber flap, very
thin, and attached only on one side. Except that it's rubber and
there's a small gap around the black rubber and I can blow the flap
out of the way in either direction, it could be a check valve. There's
no directional arrows on the nipple.

The only reference in the manual is on the repair parts schematic
where these nipples are described as: "Nipple w/Heat Traps". In the
installation section the diagram shows an arrow pointing to the hot
and cold inlets with the description: "3/4" Threaded Nipple". Nothing
about heat traps. The impression is that you could use any 3/4"
nipple.

Does anyone have any idea of the function of these special nipples and
which way they go in. I'm a little worried that the rubber flap is so
flimsy that it'll break off and end up blocking some faucet. Maybe
it's a partially disconnected washer (the hole hasn't been properly
punched out) but why would they reduce the size to 3/8"?

If no one has any good ideas, screw them. I'll just put back the 3/4"
brass nipples I removed from the old heater.



If your home is plumbed with copper piping those plastic lined nipples
are there to help prevent galvanic corrosion at the juncture between the
copper piping and a steel tank or steel nipple.

The theory is that they provide physical separation between the
dissimilar metals, filled with water. that makes for a longer path
through the electrolyte (water) with higher higher electrical
resistance, thus reducing the galvanic current and subsequent corrosion
of the steel to a much lower level than if the two metals were in direct
contact, when the length of the current path through the electrolyte is
essentially zero.

Note that the piping and tank themselves are still electrically
connected by reason of the power feed ground to the water heater and the
code required electrical grounding of the home's piping.

They work a lot better than the traditional dielectric coupligs which
have their brass and steel parts located maybe 1/16" away from each other.

As already mentioned, the flap valves are there to prevent heat loss
through thermosyphon action causing the hot water to rise out of the
tank into the piping when nobody is running the hot water.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

wrote in message
oups.com...


And while these aren't perfect in stopping all the heat, neither is a
heat trap constructed of pipe. You now have a loop of several feet of
pipe that you have to insulate, and that will still lose heat, plus
some heat does transfer through the water anyway, etc.


Several feet? What kind of loop do you think is needed? On mine there is,
at most, 24" of pipe that needs insulation. That's not 'several feet'. And
no, heat doesn't 'transfer thru the water anyway' if the loop is tall
enough. I know this because the outlet of the loop is the same temp as (or
very close to) the incoming cold water pipe.

Jeff Wisnia wrote:
wrote:
If your home is plumbed with copper piping those plastic lined nipples
are there to help prevent galvanic corrosion at the juncture between the
copper piping and a steel tank or steel nipple.

The theory is that they provide physical separation between the
dissimilar metals, filled with water. that makes for a longer path
through the electrolyte (water) with higher higher electrical
resistance, thus reducing the galvanic current and subsequent corrosion
of the steel to a much lower level than if the two metals were in direct
contact, when the length of the current path through the electrolyte is
essentially zero.

Note that the piping and tank themselves are still electrically
connected by reason of the power feed ground to the water heater and the
code required electrical grounding of the home's piping.

They work a lot better than the traditional dielectric coupligs which
have their brass and steel parts located maybe 1/16" away from each other.

As already mentioned, the flap valves are there to prevent heat loss
through thermosyphon action causing the hot water to rise out of the
tank into the piping when nobody is running the hot water.

Jeff

Ok, makes sense. But take the case of a propane WH plumbed with
PVC/CPVC. The tank ground is only through the BIP gas inlet. Are there
still galvanic currents within the WH? Is there still enough heat loss
through the PVC to be concerned with?

Bob S.

Bob S. wrote:

Jeff Wisnia wrote:

wrote:
If your home is plumbed with copper piping those plastic lined nipples
are there to help prevent galvanic corrosion at the juncture between the
copper piping and a steel tank or steel nipple.

The theory is that they provide physical separation between the
dissimilar metals, filled with water. that makes for a longer path
through the electrolyte (water) with higher higher electrical
resistance, thus reducing the galvanic current and subsequent corrosion
of the steel to a much lower level than if the two metals were in direct
contact, when the length of the current path through the electrolyte is
essentially zero.

Note that the piping and tank themselves are still electrically
connected by reason of the power feed ground to the water heater and the
code required electrical grounding of the home's piping.

They work a lot better than the traditional dielectric coupligs which
have their brass and steel parts located maybe 1/16" away from each other.

As already mentioned, the flap valves are there to prevent heat loss
through thermosyphon action causing the hot water to rise out of the
tank into the piping when nobody is running the hot water.

Jeff


Ok, makes sense. But take the case of a propane WH plumbed with
PVC/CPVC. The tank ground is only through the BIP gas inlet. Are there
still galvanic currents within the WH? Is there still enough heat loss
through the PVC to be concerned with?

Bob S.



Yes, I would expect galvanic currents within the water heater because of
the sacrificial anode which is inside the tank and intended to take the
corrosion hit and protect the task. With PVC piping to the "cold" and
"hot" tank fittings, the plstic lining in those nipples isn't
accomplishing anything to help the tank corrosionwise, but it does keep
the steel part of the nipples from corroding of course.

The anti-thermosyphon feature may save you a little bit of propane.

I don't know how different the thermosyphon effect heat loss through PVC
would be compared to copper. I've got a sneaky feeling that they may
turn out to be equal, but I'm too lazy to to the physics.

Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

"Bob M." wrote:

wrote in message
.. .
I'm in process of replacing my water heater (gas). I've got the new
one out of the carton and it's got all the normal stuff plus something
extra: a bag containing two 3/4" galvanized steel nipples. Each is 2"
long with a blue plastic lining running the length of the inside and
protruding about 1/16" at each end. If I screwed one down on the dip
tube (which seems to be the same color plastic) effectively the water
wouldn't touch the galvanized nipple. I don't know why I'd want this
on the hot side though.

Galvanized pipes rust from the inside out. Good to have both nipples plastic
lined - they last much longer.

Brass lasts even longer. I put back the brass nipples from the old
water heater. It lasted about 14 years and the nipples don't show any
sign of corrosion.

But wait, there's more. At one end of each nipple attached to the blue
plastic lining is a (also) blue plastic ring bringing the outlet
diameter down to 3/8". Inside the ring is a black rubber flap, very
thin, and attached only on one side. Except that it's rubber and
there's a small gap around the black rubber and I can blow the flap
out of the way in either direction, it could be a check valve. There's
no directional arrows on the nipple.

The black rubber thing is a heat trap. Keeps the heat inside the heater
when the thing is not being used. A good idea, but this implementation
needs work if you ask me. See below for a better way.

Why not just put in a proper check valve (brass) on the hot line?
(Personally I don't have the space--the hot and cold lines go straight
into the finished wall--but it's a thought for the future.)

The only reference in the manual is on the repair parts schematic
where these nipples are described as: "Nipple w/Heat Traps". In the
installation section the diagram shows an arrow pointing to the hot
and cold inlets with the description: "3/4" Threaded Nipple". Nothing
about heat traps. The impression is that you could use any 3/4"
nipple.

You can use any 3/4" nipple as long as it's plastic-lined. You just don't
have the heat trapping capabilities with a normal nipple.

Based on my experience the brass nipples don't need to be plastic
lined.

Does anyone have any idea of the function of these special nipples and
which way they go in. I'm a little worried that the rubber flap is so
flimsy that it'll break off and end up blocking some faucet. Maybe
it's a partially disconnected washer (the hole hasn't been properly
punched out) but why would they reduce the size to 3/8"?

No, the rubber flap is the heat trap mechanism. I don't think it matters
which way they go in, if it did the mfgr would likely have arrows painted on
them to indicate the direction of flow.

Yeah, right! This is a manufacturer who obviously didn't think it was
worthwhile to explain what you've just explained. I doubt that I'd
trust them to remember to put arrows on the nipples.

However, I think the things are
likely to be completely ineffective in a few years after the rubber flappers
get permanently bent in the outflow (hot-side) or inflow (cold-side)
directions, or they break off. Plus, they don't truly stop all the heat
from getting out.

A better solution is to make a heat trap out of copper pipe. This kind of
trap is nothing more than a loop. Heat rises, but it doesn't sink, so the
heated water will stay in the tank when hot water is not being used and it
won't radiate heat out the first 10 feet or so of pipe coming out of the
tank.

I have such a trap on my tank and the outlet side of the heat trap is as
cold as the incoming cold water pipe if the tank has been sitting for a
while. My loop was 1/2" copper pipe rising 12" out of the heater's hot
side, then across 2", then back down 12" and out to the house. The length
of the up & down sides of the trap do matter, longer is better up to a
point. 6" probably isn't long enough to truly keep the heat in. (If
necessary, the same kind of trap can be applied on the cold water side, but
it probably isn't necessary; the dip tube does the trick there.)

Because this involves laws of physics, it will always work and it will never
have a piece break off and plug up something. Supposedly you can take a long
length of that so-called "flexible" copper pipe and make a loop out of it -
it would do the same thing - but have you ever tried to bend that stuff?

I thought the flexible copper type had been banned? Anyway, my big box
stores only sell the braided stainless steel type and I can't see
bending one of those into a loop.

Thanks for the info.