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Does a Washing Machine waste have to go through a P trap with a long upright as I have traditionally seen? or can it be fitted to a spare Appliance Connector leading into the Bottle Trap under the sink?

Under my sink I have a Bottle Trap with an Appliance Connector (capped off) and a Tee Connector (for a 1.5bowl sink) that also has an Appliance Connector on it.

Im sure I've heard something about a washing machine waste needing venting? is this why the pipe is normally pushed down a P trap?

....just to clarify, I will have a dishwasher connected to one of the appliance connectors, so can the washing machine connect to spare connected thats currently capped?

I doubt i'd ever have the two appliances running together, but either way they'd both run down the same 40mm waste and bottle trap.

The washing machine does need venting to stop it siphoning water back into the machine.

You can connect the outlet to the trap as you asked without any problem.

The plughole or overflow will act as the vent.

Just make sure the washing machine hose is as high as possible under the sink so as to avoid water from the sink feeding down into the machine.

i read on the forum somewhere that all bottle traps are anti syphon, so can someone explain the difference between:

[url]http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=101958&ts=48115&id=19709[/url]

...and...

[url]http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=101958&ts=48169&id=48341[/url]


I work as a shower designer and know that we have to be careful with shower trap flow rates, will normalbottle trap handle both a small dishwasher and washing machine dumping its waste at the same time??

Is it just me, or are all the URL's not working?

Post the Screwfix product code manually please.

....it wasnt just you, the links didnt work.

One link is for the screwfix anti-vac trap (screwfix 19709) and the other is a standard trap (screwfix 48341)...I read in the forum all bottle traps were anti-vac, so wondered what the difference was?

I have just got a standard trap, and im concerned it wouldnt manage with the flow of both dishwasher and washing maching dumping waste through a 40mm bottle trap at the same time (i've read too many horror stories on the forum!?!?)

I'll def take your advice Marrtin and make sure the hose is as high as possible with one of the sink plug holes open (for some reason i dont have an overflow)

As you are aware, a normal trap works by creating a seal using water to prevent odours from entering the room. In certain conditions this water can under vacuum be drawn out of the trap leaving it empty, and consequently leave a free passage for foul air.

To prevent this, anti siphon or anti vac traps have a one way valve fitted that allows air to enter the trap on the drain side and remove the vacuum which ensures the water seal is not broken. It is not usual to fit these unless this symptom is experienced.

You can get traps that have two connections - one for a washing machine, the other for a dishwasher say. In the past I have tested by draining both appliances together, and the sink still empties at speed!!

I always use this type of installation if the washer or dishwasher is next to the sink.

This is really useful information, thankyou.

I have now completed everything I needed to do, the dishwasher and washing machine will be installed after Christmas (im going to take advantage of the Jan sales) and wanted to save plumbing twice!

Thankyou so much for your help, I now have a kitchen I can use again!