Washing machine waste

We had some temporary plumbing done for connecting up a washing machine. However, when I now come to install the washing machine I find that the waste pipe to connect up to looks like 18-20mm plastic pipe and I don't know how to connect this to the waste pipe from the machine as this would typically go into a stand pipe. The current plumbing runs across our kitchen (behind cabinets) to our sink waste. This is only in place for about 6 months while an extension is built. Any suggestions on how I connect the waste pipe to the 18mm plastic pipe? Is this an ok temporary setup or are we likely to have problems? Would we be better off swapping this with the dishwasher which has more regular plumbing? Slightly worried that it won't be able to cope with the amount of water used by the washing machine.

That sort of pipe diameter is typically for an overflow from somewhere or maybe a boiler condensate drain.....is it possible to connect into your sink drain connection?
Most satisfactory if its possible!
John

Hi, the pipe we're trying to connect to does link to the sink drain. We had it fitted specifically for installing the washing machine so I assume the plumbers fitted something appropriate. The problem now is that I can'T actually connect the washing machine waste pipe to the newly fitted pipe work. I need something that will enable me to connect the end of the washing machine waste pipe to this 18-20mm pipe. What can I get for that?

Beyond that my question was really whether this sounds like a workable/sensible (but albeit temporary) setup. I guess it is otherwise I assume the plumbers would have advised against it?

So, how do I connect the pipes?

My best advice is to ask the 'plumbers' to go out and buy the correct fitting for connecting a washing machine to overflow pipe and see how they get on with that.

21.5mm pipe isn't sufficient for a washing machine's output flow rate.
Find another way!

Could we use this for our dishwasher and put the washing machine where that is. The dishwasher is currently connected directly to the sink waste?

I assume the output flow rate of a dishwasher is less than that of a washing machine?

The volume is definitely less, but depending on the model the flow rate may be the same or as close as makes any difference - it just won't last as long.
The bore of that pipe still isn't sufficient.

Have you got any plans or photos of the room layout so we can advise an alternative?

No, don't have any plans but I can probably put some together. However, this setup is only temporary until we have an extension built next spring/summer. At that point the dishwasher will probably be replaced anyway whereas the washing machine (which is brand new and relatively expensive) will not.

The current setup is that we have the dishwasher to one side of the sink with a fairly standard connection to the sink waste trap. This has worked fine for sometime. The washing machine was mean't to go in its new temporary spot about 3 metres from the sink with new pipe work running through or behinds cabinets. This is the 21.5mm overflow type pipe referred to earlier. Given this setup I am now thinking it would be best to locate the washing machine where the dishwasher currently is and the dishwasher where the washing machine is meant to go. This is based on the fact that the dishwasher uses less water, is used less than the washing machine and is cheaper and more likely to be replaced when we redo the kitchen when the extension is built. Does this make sense?

One thing I don't understand is why 21.5mm pipe is not sufficient given that the flexible waste pipe actually attached to the washing machine (and dishwasher) is about this diameter (which is why I am having trouble connecting it). Surely the flow rate will ultimately be determined by the narrowes part of the waste pipe and if the initial flexible hose is this diameter then how can it be a problem if the rest is? Am I missing something here?

If anyone can tell me whether my proposed setup is ok that would be great.

The nominal 21.5mm waste is fine - it's quite common to attach washing machine waste to traps fitted with spigots of around this diameter.

That said it is important that, however temporary, the waste is connected correctly to prevent backflow of foul water into the washing machine.

What's at the other end of the recently installed pipework and how far does it run?

Thanks for the info. It runs for about 3 metres (approx) and connects to the trap under the sink. This dishwasher connects to the same trap but without any additional pipe work required.

So, are you saying that there is no need to swap the dishwasher and washing machine locations as 21.5mm pipe work is fine for a washing machine?

In terms of correct fitting, does it need to go into a standpipe first or does it simply need to have a sharp vertical rise and then drop as per dishwasher fitting? Currently it would rise immediately to almost the height of the machine and then drop slightly to go through a hole in the side of a kitchen cabinet. This is where it would then connect to the 21.5mm pipe which then runs in a downward slope until it reaches the sink trap (which itself then runs directly outside to the drain).

Does this sound ok?

It would need joining with a jubilee clip etc, if it had an air gap it would overflow.

I hope it's all been solvent welded or you could have a deluge. Even so it's less than ideal.

A rise to worktop height aand back down again would be correct.

Less than ideal but ok as a temporary setup?

Would I still be better off switching the washing machine and dishwasher or do I not need to?

It will be fixed with a jubilee clip and the pipe work has all be properly done.

The waste goes directly up to near worktop height but then only drops a little (not down to worktop base). Is that ok?

Should work, but can't guarantee.

The washing machine and dishwasher probably pump about the same peak flow so no point swapping.

I would have thought an extension hose would have been the simplest solution.

Assuming you mean up to worktop height then down to trap level, that's how it is normally done.

Thanks - will give it a try.

Appreciate all the advice.