Questions on water supply & waste for washing machine & dishwasher

[Adam Funk]

I need to rearrange some of the plumbing under the kitchen worktop so I can push the appliances back further in the slots, & I have a few random questions about the input & output.

We have a cold-feed-only washing machine in place & a cold-feed-only dishwasher on order. There are 2 cold connections & 1 hot one; the hot one has never leaked yet, but I'm a little nervous. Is there a secure cap I can put over the unused hot connection? Or should I just remove it & cap the hot pipe off because cold-and-hot-feed appliances are very unlikely to appear again?

(The strange thing is that when we moved into the house, there were 2 hot connections & 1 cold one.)

What do I need to do (apart from turning the gas off) to make it safe to solder a joint on a copper water pipe a few cm away from a gas pipe? Or should I just use a compression fitting?

The two waste pipes currently meet at a T above the kitchen floor; the merged pipe goes under the floor then runs under the kitchen and through the wall, where it opens over a drain. I haven't been under the kitchen floor in a long time, & I can't remember whether there's a trap in there.

I plan to change it so two waste pipes both go vertically down through the floor and meet underneath, then run to & through the outside wall (using solvent-weld). Do I need separate traps for each pipe? Should I leave a trapdoor under one of the appliance positions in case I need to unblock them later?

Thanks, Adam

[Tim Watts]

On Thursday 29 August 2013 12:15 Adam Funk wrote in uk.d-i-y:

3/4" BSP cap with washer. Available in most fine plumbers merchants and maybe even B&Q.

That would also be a safe bet. I have not plumbed hot to my machines.

If you are not near a gas joint (that teh heat could disrupt or melt), no major precautions are necessary beyond standard good practise - but I would turn of the gas anyway.

Use a heat shield mat - which you want to do anyway to protect the wall.

But a compression joint would be just as good if soldering near gas makes you nervous. Or even a push fit end cap.

No. I have a combined trap for 2 machines. However my trap was made out of bits of 50mm solvent weld plumbing with screw caps on tees at one top and one bottom bend to enbale access for unblocking.

So if using one trap make sure it can take the flow of 2 machines at once (sod's law says they will align at some point!).

Either that or have a method for being able to pull a machine out - eg sit it on rollers or have some scraps of hardboard stored away.

Cheers

Tim

[Java Jive]

No particular comment to make about the feeds.

There are at least two primary purposes to a trap ... 1) To keep out drain smells 2) To trap objects that may cause a blockage ... but a third is to prevent waste from one source adversely affecting the others.

I would say that you need a trap for each individual item whether it be sink/basin, or one or other machine.

This is based on formerly plumbing in a dishwasher into a system that already had a standpipe for a washing machine. There was a bottle trap under the sink, and a u-trap for the standpipe, so I inserted a second standpipe for the dishwasher between the existing washing machine one and its trap, expecting them to share the trap quite happily. However, what actually happened was that soapy water from the washing machine gradually caused froth to rise up the second standpipe and overflow all over the kitchen cupboard. I had to insert an expensive waste flap-valve in the dishwasher standpipe to prevent this happening.

As above, most definitely yes.

Some sort of easy access might be wise, but see what others say.

[Adam Funk]

And two "slots" for appliances under the worktop. Did hot-feed-only appliances ever exist?

[Adam Funk]

Excellent, I'll probably use that.

I have one of those, & meant to mention it, but it disappeared when I was rearranging those sentences!

I'm not 100% sure what you mean but I think it's something like this (where XXXs are threaded caps)? If so, I like it.

in | | | | |XXX| | | | | | | | ----- | | | out | | | ----- | | | | | | | | | ----- | | | | --------| | | |XXX|

Well, I've been running a washer-dryer & a dishwasher through the existing set-up, which I'm sure has at most 1 trap, for 10 years.

[Tim Watts]

On Thursday 29 August 2013 15:02 Adam Funk wrote in uk.d-i-y:

and one bottom bend to enbale access for unblocking.

Yes - pretty much. Mine is under the stairs behind the machines so very accessible :)

[John Rumm]

I have not seen one start leaking without provocation. ;-)

If you are that fussed, a compression stop end may mate with the existing backnut and olive from the tap.

Stick a couple of layers (i.e. folded) heat mat in the way to protect the gas pipe.

You don't absolutely need two separate traps, although I would be inclined to fit them, and keep them both above the floor where they can be dismantled and cleaned. If you join both your downpipes to the exit pipe with swept tee fittings, then you can stick a rodding eye into the other side of the end tee. That should cover most options.

[Adam Funk]

I like the design. From looking at Wickes &c., it seems that the Ts & end caps are cheaper than ready-made traps (& it's hard to find traps for solvent-weld installation).

Lucky you.

[Adam Funk]

I think I'll go for that, although #2 isn't relevant here: the existing pipe runs out the wall and opens over a grate outside that goes to a 4" pipe.

[Adam Funk]

The provocation I'm concerned about is that an appliance might bump into the red plastic lever. It hasn't happened yet, I have to admit, but I figure I should prevent it while I'm tidying up back there.

I've looked at the situation again, & the cold pipe (which may need some soldering) is above the hot pipe (which doesn't need soldering), which is in turn above the gas pipe.

Thanks for the tips. I don't have room to build the traps above the floor, because of the tight space & difficulty I have in stuffing the appliances back into the space. (I had to swap the positions of the washer-dryer & dishwasher last summer when we replaced the washer-dryer, because the new one was 600 mm from front to the

*middle* & the top of the back, whereas the previous one had been proud near the top of the back only.)

[Adam Funk]

Thanks for all the advice. I ended up with a fairly nice job, & the appliances fit better under the worktop. I didn't have to do any soldering in situ --- I just undid a compression fitting, modified the pipework downstream of it on a workbench, & screwed it back on.

As it turns out, the old "trap" consisted of an elbow under the floor with the horizontal-ish pipe bent upwards from the elbow to the hole in the wall. There are now 2 traps inspired by Tim's suggestion but simplified (1 T & 1 unscrewable end cap, "X" below) to fit in the spaces available. (Each "in" pipe is right against the wall, & the out pipes are just under the joists.)

in | | | | | | | | ---------------- | | | out | | | ------------ | | | | | | | | | ----- ---- | X ----------------