Re: Washing Machine backfilling

[Bob Minchin]

Andrew McKay wrote:

> > I've just been presented with an interesting problem, I wondered > > whether others might have found a similar situation? > > > > The situation is a washing machine and dishwasher which are connected > > to the drain pipe via a Y tee-piece into a 15mm pipe. No problems with > > that, all working fine. > Surely these 15 mm T pieces are for combining inlets? > Sounds like a bad idea to me. Each should have its own 32mm waste > connection. > I'm surprised there isn't trouble already.

You took the words right off my keyboard Bill!

This has got to be a disaster waitng to happen unless the OP has his inlets and outlets confused.

Bob

[Andrew McKay]

Nope. The inlets are hot and cold fills which have the usual blue and red taps on. Trust me, I know my inlets from my outlets :)

The outlets from the two appliances already installed connect into one of these Y tee pieces:

Y is bolted on (as in compression fitting) the end of a 15mm pipe, which then finds its way under the sink to connect to the usual plastic pipework to the drain system.

I've been asked to add a 3rd outlet to this arrangement. I had wondered whether there were connectors which include some sort of blowback prevention valve - though I can't recall seeing anything like that. My concern was raised when I thought this through, I can't ever remember seeing even two appliances dumping thru a common piece of

15mm pipe, so three makes it an interesting proposition :)

I know one of the existing connections is a dishwasher. I didn't think to ask what the other one was - the dishwasher is the only appliance of any size on that side of the kitchen. Time for a question methinks.....

Andrew

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[David]

You can certainly (or at least could) get kits from B&Q which included valves to prevent backflow; I once installed one of these in a previous home, when there was no easy alternative. Kit consisted of a plastic saddle which you bolted over an existing waste pipe, providing a threaded tee-off bit (sorry hard to explain!). You screwed a cutting tool down the tee, which opened a hole into the waste pipe, then attached an adaptor to the tee, to which was connected the waste hose to the new appliance. Within said adaptor, there was built in a spring-loaded one-way valve (looked like a valve on a car cylinder head) - this was supposed to prevent backflow.

Having said that - I *think* a lot of appliances already have valves to prevent backflow prevention built in? But you couldn't assume that. I'm sure somebody else will know more than me.

Finally, I'd share the other respondent's concerns at having three appliances emptying down one pipe. What happens if all 3 decide to empty at once? Maybe you could recommend your customer has a proper job done, but if they insist on the bodge, you could install it with a disclaimer that they should never use all machines at once?!

David

[Bob Minchin]

Apologies for doubting your ability to distinguish between inputs and outputs.

In my diy /domestic experience, I've not seen a outlet hose other than the 'hook over a vertical open drain pipe'type and wonder still if it has been a diy bodge connecting the outlet to the Y adaptor that you illustrated via screwfix. I could quite imagine a buildup of scum etc from the washing machine and dishwasher grease etc gradually bunging up a cold 15mm coper pipe.

From your website I see you are putting you DIY skills to good use and maybe to preserve/build a reputation you might be best to advise replacement with conventional drainage arrangements with anti-siphon air gaps and traps. If on the otherhand these appliances are designed to discharge in this way and I'm talking thru my ar*e, then I'm sure someone will say so and we will have both learned something.

Good Luck

Bob

[Andrew McKay]

No problem - we are all friends on this forum, and I most likely didn't explain myself too well :)

Andrew

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[Chippy]

Then it is cobbled up.

No appliances should be emptying through 15mm pipe.

Most washing machine pumps have a flap valve to reduce the risk of back-flow.

In your original post you said that it was a washing machine...

[Andrew McKay]

I'm at it again aren't I? Not explaining myself very well..... ;)

Washing machine is to be moved across the kitchen to where there is this marvellous christmas tree arrangement for the drainage. There's a dishwasher there currently. And another device. It's that other device that I can't recall what it is - I literally didn't investigate.

Andrew

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[Christian McArdle]

I'm also amazed it works at all with 15mm pipe. All my washing machine and dishwasher drainage has always been through 40mm plastic. 15mm is fine for water under pressure. Waste with no pressure to speak of needs waste sized pipe, not microbore.

I'd redo the entire lot in waste pipe immediately.

Christian.