Long story cut short - very old building, second hand kitchen, new
dishwasher.
Without going into details, there are two good reasons for not being
able to run the recommended 32mm standpipe behind the cupboards and
through the 2'6" thick outer stone wall, in which a 23mm hole could
easily be made, but a 32mm one would be "a nightmare" (plus I'd have
to hack holes out of the back of the kitchen units.

One builder and one plumber can't see any way round it other than to
just have a 23mm wastepipe.

As long as there was a good fall (there would be - 600mm over 6 feet -
mixing my measurements here!) and the top of the pipe was the 800mm
the manual specified, can anyone see anything wrong with it?

The entire pipe run will be sealed, so no trap needed inside.

I guess what I'm trying to get at is - it's not ideal, but in the case
of their really being no other option, is there any reason it won't
work? And I've already thought about build up, but as the wash is
about 90 degress and full of evil chemicals anyway, I can't see it
getting the kind of fatty deposit buildup associated with cooler sink
water and normal "hand strength" detergent.

Just to pre-empt questions about building and water regs, they're not
going to actually fit it themselves, it was left as "regulations, see,
but if you thought about it, you could...", and the outflow WILL be
teed into the sink waste, just outside instead.

On Jul 9, 2:37*pm, lardconcepts wrote:
Long story cut short - very old building, second hand kitchen, new
dishwasher.
Without going into details, there are two good reasons for not being
able to run the recommended 32mm standpipe behind the cupboards and
through the 2'6" thick outer stone wall, in which a 23mm hole could
easily be made, but a 32mm one would be "a nightmare" (plus I'd have
to hack holes out of the back of the kitchen units.

One builder and one plumber can't see any way round it other than to
just have a 23mm wastepipe.


Would it help to use two 23mm pips in parallel to give the same flow
area as a 32mm pipe?

Robert

"The entire pipe run will be sealed, so no trap needed inside."

Isn't this likely to cause siphoning?

On Jul 9, 2:42*pm, "John" wrote:
"The entire pipe run will be sealed, so no trap needed inside."
Isn't this likely to cause siphoning?

No, the pipe will be draining into a gulley-style drain, so as there's
an air gap between the two, there's nothing to siphon.
I know this isn't "current regs", but the sink has drained into it for
the last 40-odd years or so, and it drains into a private septic tank
anyway (ie: it still goes to the foulwater drain, not a rain soakaway)
really I can't see the problem.

On Jul 9, 2:41 pm, RobertL wrote:

Would it help to use two 23mm pips in parallel to give the same flow
area as a 32mm pipe?

Hmmm, subtle idea, but even drilling one hole through the wall is
going to be enough aggro. If it has to come to it, I suppose it's an
option, but drilling through stone-wall is going to be bad enough as
it is.

On Thu, 9 Jul 2009 07:01:12 -0700 (PDT) someone who may be
lardconcepts wrote this:-

"The entire pipe run will be sealed, so no trap needed inside."

Isn't this likely to cause siphoning?

No, the pipe will be draining into a gulley-style drain, so as there's
an air gap between the two, there's nothing to siphon.

Imagine the situation where the machine has just pumped out the last
water. There is now a pipe full of water propelled by the pump down
a "good fall".

Depending on the arrangements inside the machine one of two things
is likely to happen. If you are lucky the water will draw air into
the pipe behind it, drawing the air through the pump. This will
empty any trap in the machine.

If you are unlucky the water will not be able to draw air behind it
and will not be able to draw air along the top of the pipe (as it
would be able to do with a larger pipe). In this case your pipe will
be flattened by atmospheric pressure on the outside of the pipe.

Either find out what is inside the dishwasher, or arrange an air
admittance valve where the end of the hose and the start of the
fixed pipe starts. Do make the long run in proper pipe, suitably
supported and with easy bends if there are any (to minimise back
pressure), I would use copper pipe.

Done properly there should be no problem even with decades of use.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Can you start with a vertical run of 32mm and then join that to the
23mm? I ask as I seem to recall that you get a much greater flow rate
through a given run of downpipe after the initial section in which the
flow may be especially turbulent. That applies in spades with rainwater
downpipes (which have a greater capacity if they collect water from a
wider inlet than from - say - juts a running outlet.) Might it also
mean you can avoid the issues of siphoning by using a conventional pipe
hooked into the 32mm pipe?
--
R

"lardconcepts" wrote in message
...
Long story cut short - very old building, second hand kitchen, new
dishwasher.
Without going into details, there are two good reasons for not being
able to run the recommended 32mm standpipe behind the cupboards and
through the 2'6" thick outer stone wall, in which a 23mm hole could
easily be made, but a 32mm one would be "a nightmare" (plus I'd have
to hack holes out of the back of the kitchen units.

One builder and one plumber can't see any way round it other than to
just have a 23mm wastepipe.

As long as there was a good fall (there would be - 600mm over 6 feet -
mixing my measurements here!) and the top of the pipe was the 800mm
the manual specified, can anyone see anything wrong with it?

The entire pipe run will be sealed, so no trap needed inside.

I guess what I'm trying to get at is - it's not ideal, but in the case
of their really being no other option, is there any reason it won't
work? And I've already thought about build up, but as the wash is
about 90 degress and full of evil chemicals anyway, I can't see it
getting the kind of fatty deposit buildup associated with cooler sink
water and normal "hand strength" detergent.

Just to pre-empt questions about building and water regs, they're not
going to actually fit it themselves, it was left as "regulations, see,
but if you thought about it, you could...", and the outflow WILL be
teed into the sink waste, just outside instead.

Been there seen that with a dishwasher outlet plumbed in 22mm copper as
being the only way to get the waste behind a kitchen unit and through a
limestone thick wall.

Apparently worked fine for couple of years (2-3 ?) then dishwaser had issues
emptying. Fault finding guide said "blocked drain/outlet pipe" which it was.
Removing the fitted dishwasher and using drain unblocker got it going again
but blocked again in a month or two. Also had issues connecting the drain
hose to 22mm pipe in a leak free manor. It always had a slight leak.

The 22mm pipe was changed to a longer washing machine type hose (5 meters ?)
and that was better but eventually leaked at a tight bend after about 5
years.

The whole lot was then redone correctly in 32mm plastic pipe, which involved
removing kitchen units from under the work top, chiseling the wall to get a
32mm trap in and drilling a 32mm hole.to outside.Worked fine for years no
issue until dishwasher died !!!.

I have personally changed a dishwasher hose from the supplied 1.5m hose to a
longer hose 3m (involves getting inside the dishwasher to attach the hose)
so the outlet hose could pass behind a kicthen unit to the drain spigot on
the kitchen sink U bend. Still working as far as I know.

On Thu, 09 Jul 2009 14:52:49 GMT someone who may be "neverwas"
wrote this:-

Can you start with a vertical run of 32mm and then join that to the
23mm?

Larger pipes going into smaller ones are not appreciated. I would
want to do some calculations before installing one.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

In article ,
lardconcepts writes:
Long story cut short - very old building, second hand kitchen, new
dishwasher.
Without going into details, there are two good reasons for not being
able to run the recommended 32mm standpipe behind the cupboards and
through the 2'6" thick outer stone wall, in which a 23mm hole could
easily be made, but a 32mm one would be "a nightmare" (plus I'd have
to hack holes out of the back of the kitchen units.

One builder and one plumber can't see any way round it other than to
just have a 23mm wastepipe.

As long as there was a good fall (there would be - 600mm over 6 feet -
mixing my measurements here!) and the top of the pipe was the 800mm
the manual specified, can anyone see anything wrong with it?

The entire pipe run will be sealed, so no trap needed inside.

I guess what I'm trying to get at is - it's not ideal, but in the case
of their really being no other option, is there any reason it won't
work? And I've already thought about build up, but as the wash is
about 90 degress and full of evil chemicals anyway, I can't see it
getting the kind of fatty deposit buildup associated with cooler sink
water and normal "hand strength" detergent.

Just to pre-empt questions about building and water regs, they're not
going to actually fit it themselves, it was left as "regulations, see,
but if you thought about it, you could...", and the outflow WILL be
teed into the sink waste, just outside instead.

I have a dishwasher installed some distance from the sink/drain.
I used 21mm solvent weld overflow pipework around under the units,
probably a 5m run, before it rises up into the cupboard under the sink
and enters the sink waste before the U-trap and that forms an air break.
It's worked fine for 9 years. The dishwasher is specified to allow the
outlet to be pumped quite high (IIRC, high enough that you could have
it in a basement, pumping out to a waste on the floor above, although
I'm not using that capability). However, this means the dishwasher
does have a non-return valve in the waste outlet, but that's not really
relevant in the situation I have installed it.

IME, dishwasher detergent is excellent at cleaning the pipes it runs
through. For a brief period, I had it pumping out into the sink, and
I never had to clean the sink during that period -- it was always
bright and shiney!

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Jul 9, 2:37*pm, lardconcepts wrote:
Long story cut short - very old building, second hand kitchen, new
dishwasher.
Without going into details, there are two good reasons for not being
able to run the recommended 32mm standpipe behind the cupboards and
through the 2'6" thick outer stone wall, in which a 23mm hole could
easily be made, but a 32mm one would be "a nightmare" (plus I'd have
to hack holes out of the back of the kitchen units.

One builder and one plumber can't see any way round it other than to
just have a 23mm wastepipe.

To follow this up, so you can all say "told you so!", after a couple
of quotes around £200, I decided to try it myself, and rented £30 of
drill and diamond core.

Started at 8pm, should've taken about an hour to go through the wall.

Except..rubble and stone wall. Once I'd put the extension bar on, it
was still going OK until it snagged on something. I'd been clearing it
regularly, taking it slow, letting it take it at it's own speed. I
tried to pull it back out, but what had happened was some rubble had
fallen onto the extension bar, trapping the drill.
I'd measured it, I was ONE INCH from the other side of a 20" wall.
Totall stuck, wouldn't move or rotate at all.

After about an hour of trying to free it, I got a grip wrench (the
motor / clutch was just stalling) and after much to-ing and fro-ing
managed to free it by using all my might, putting all 14 stone of me
on the wrench having propped it below so the force would be
rotational, not downwards.

It was about 11pm when it went "ping" and would turn again. However,
it just wasn't going any deeper now.
In hope and desperation, I just kept pushing for about half an hour,
but nothing. Probably one of the best ideas I've ever had struck me -
I went outside, felt for the "warm bit" on the wall (it was a cool
night), got a normal drill, drilled loads of little holes, and bust in
with a crowbar.

By 1am, I'd got the core drill out from the other side, fed the pipe
through,and inhaled enough dust to setup a small cement factory in my
lungs.
To my horror, I also found that in freeing the drill, I'd bust off one
of the diamon teeth. And this was a very expensive drill - even with
the hire place taking pity on me and only charging me cost price (he
showed me his trade list when I still baulked at the price) AND taking
into account discount of existing wear, the whole episode ended up
costing me £90 inc.

Bottom line is, I still saved over £110, however it's one learning
curve I don't ever want to repeat in a hurry!