No Trap on Washing Machine Waste

[PhilipKS]

Hi All
Just taken out an old washer to find that the standpipe waste is just connected into T-fitting onto a horizontal waste pipe. The waste pipe just goes through the wall and discharges over an open gully drain (no soil connection etc). There are two sinks (cloakroom hand basin & utility) that discharge via traps into the same pipe.

Never had any problems with smell or poor flow. Pipe config is going to prevent me fitting an s-trap. Suppose I could use one of those Hepworth vertical 40mm air admittance things I've read about…but if it ain’t broken don’t fix it etc.

Do I really need a trap if there is no way for foul gases etc to back up the pipe?

May thanks
Philip

 

[kevindgas]

although a trap is always preferable you can do it without

get a connector for the washing machine hose
Graham's part no. PBMCT229 Mcalpine straight WM nozzle this and a 40mm straight compression fitting or 40/32 compression reducer if 32 mm pipe will give you a sealed pipe entry

 

[John506]

Unless your open gully gets really smelly then there is no smell to travel back up.

I would go with the if it isn't broke don't fix it

 

[Slugbabydotcom]

Them purpose made washing machine tees usually have a non return device in them.
Apart from that you usually find that after the pump has stopped working at the end of a cycle theres always a little bit of water that runs back down the pipe and forms a trap seal after or at the pump.