Dishwasher Wastepipe

[bigwillycomputing]

Hello

We've just moved into a 1930's house and my wife wants a dishwasher installed :-(.

I'm ok with the input water feed, but the wastepipe is causing me a problem.

The recess for the washer is a "standard" 600mm wide x 850mm high counter top. At the back is a 9 inch solid external wall with direct access to the drains.

My problem is that there is no space behind or to the side of the appliance to contain the trap. Also, its located a good distance away from the sink so tapping into the waste there is not possible.

My question / solution is:

Can I feed the waste through the external wall and have the trap on the outside of the building? If so, can I get away with a pipe smaller than 40mm for the journey through the wall as long as it drops into a 40mm pipe on the outside?

Kind regards

Alun

[David Hansen]

On Mon, 4 Feb 2008 02:25:39 -0800 (PST) someone who may be [e-mail] wrote this:-

What sort of drains are they and what do you mean by direct access?

If there is a gully outside the wall, what is it connected to? What is connected to it may give you a steer, but someone may have made the wrong connections in the past.

The dishwasher outlet must go to a sewer, not something provided for rainwater. Depending on whether the house is in a rural area or a built up area it may be possible to guess, but it is better to be sure.

Minor details on how to make the connection only follow on from the major detail of making sure the connection is to the right drain.

[bigwillycomputing]

Thanks for the reply.

I'm not sure if this because I'm in a rural area but, yes, it will plumb into the sewer (because its all we have here).

On the external wall is the soil pipe for the upstairs bathroom and alongside it is a drain for the rainwater, washing machine and sink pipework. I've checked the adjacent man-hole and everything gets directed to the sewer pipe.

[Dave Liquorice]

See other post about the suitabilty of the drain outside. This waste water needs to end up in the foul water drainage system not rain water.

Trap outside, I wouldn't it will freeze and the first thing you know about it is when the dishwasher pumps out all over the kitchen floor...

[David Hansen]

On Mon, 4 Feb 2008 03:22:33 -0800 (PST) someone who may be [e-mail] wrote this:-

If this is close enough to connect into outside, why is it not close enough to connect into inside? Is it that the sink pipework slopes away from the dishwasher position?

[bigwillycomputing]

No - the sink and washing machine are in an extended part of the kitchen against a southfacing wall. The waste from this is directed outside, then around the outside wall back to the drain. This run is approximately 4-5 meters.

I can't easily plumb to the trap under the sink because I have the stub of the old house wall, 3 fitted units and a cooker to get behind.

The most suitable sewer drain is directly outside where the dishwasher wants to go. The only problem is space for the trap.

Kind regards

Alun

[RobertL]

is it really not possible to have a trap inside the house right behind the dishwasher. usually these machines have some space behind them even though their tops reach the wall.

Robert

[David Hansen]

On Mon, 4 Feb 2008 04:04:11 -0800 (PST) someone who may be [e-mail] wrote this:-

I would ponder over fitting a trap inside some more. There are places a traditional standpipe could go in most locations.

If it really isn't possible then, assuming the dishwasher has a built in trap, I might consider putting a 40mm pipe through the wall and into the gully, below the grid but above the level of the water standing in it. An adapter from the hose to the 40 mm pipe could then be fitted. However, this would take a similar space to a standpipe.

Small diameter pipes outside are bad news, especially in winter.

[F]

Is there space to build a trap out of 40mm pipe and three elbows? It worked for me as the sides below the top of the machine, and the bottom weren't as deep (back to front) as the main body.

I've tried, and failed, to draw in ascii art so: vertical pipe (long/high enough to take the initial surge as the machine pumps out), elbow to turn it parallel to the wall, short horizontal pipe, elbow to turn back up the wall, short vertical pipe parallel to the first, elbow to turn it through the wall, pipe through the wall.

HTH

[bigwillycomputing]

Hi F (and everyone)

I think that's what I will have to try. I've spoken to a plumber acquaintance who said that an in-line trap may also be used if the U aspect of the trap is the problem.

I think I'll glue something up and give it a try.

Many thanks for the responses.

Alun

[John]

Have a close look at the dishwasher - as Robert said - many are not as deep as the dimensions state as they have a recess for the plug, hoses and drains

[Dave Liquorice]

One could but why bother when things like:

available off the shelf. You really aren't going to get a slimmer than that the outlet collar can be into the wall so all you need is 50mm clearance at the back of the machine (10mm leeway).

I wonder if the OP has 500 mm deep worktop and a 600mm deep machine, that does fup things up if you want the machine flush to cupboards doors at the front.

[F]

That's fine, but what I was describing would allow the OP to build something that fitted his circumstances exactly rather than relying on the flexibility of the Screwfix product.

[Si]

Ahhh, that's why our d/w washer sticks out - get used to it after a while. Must remember that when I get the tuit to change the surfaces.

[Andy Hall]

Having a trap outside is generally a bad idea because of freezing. Then you would have a flood in the kitchen. Ex dishwasher water is not that pleasant.

You might be able to get away with a HepVO inline trap. These are manufactured by Hepworth, have a collapsing soft plastic sleeve inside and do not retain water. You *might* be able to get away with one of these outside but better inside. These are not significantly deeper than the pipe connecting them, so it should be possible to site the whole assembly internally.

Definitely don't use a smaller diameter through the wall.

[bigwillycomputing]

Hi

Just wanted to thank everyone for their contribution to this. My key conclusions from all the sound advice given was that (a) it is important to use a 40mm waste pipe through the wall and outside to avoid freezing (b) keeping the trap indoors is highly preferable

For the record, I fitted things today in a text-book fashion. I had no clearance behind the machine for the trap, but used a small space to the side of it. It's tight, and care is needed when shifting the machine but its looking ok.

Many thanks again to everyone.