Long waste pipe run aav and or antivac trap

[Matt0029]

I have a long waste pipe run that is out side of the recommended distance of 4 meters for 50mm pipe. It only has one appliance on it. But because of the length of the run I want to stop self syphonage of the trap. Is there any benefit of fitting a trap with and anti vac adapter or anti vac built in. The a larger aav after the trap to allow more air in to help discharge? Or would they counteract each other? Thanks

 

[king of pipes]

A constant fall is vital it may help to equal out the pressure created and aid a quieter discharge and less gurgling , when you say appliance do you mean washing machine ? Dishwasher ? If the answer yes then surely a stand pipe is all that's needed as theres a air break ? What's you connecting to ?? . Kop

 

[snowhead]

Unless you've got a bath discharging into the 50mm and lots of elbows in the run you'll struggle to get sufficient volume to create a large enough plug of water to create suction.
As K-O-P, steady fall and bends not elbows.

 

[Ric2013]

A constant fall is vital it may help to equal out the pressure created and aid a quieter discharge and less gurgling , when you say appliance do you mean washing machine ? Dishwasher ? If the answer yes then surely a stand pipe is all that's needed as theres a air break ? What's you connecting to ?? . Kop

Surely not? If there were siphonage, you'd siphon out the trap below the stand pipe allowing foul air to enter the building.

In any case, if you want to comply with the recommendations of ADH, then secondary vent, not AAV etc is the only way to go. But as ADH is a recommendation not a rule, if the pipe run is well designed then it may well be that the trap will not suffer from siphonage and that no device is required. I'd argue that if you tested the branch for trap siphonage and it passed, Part H will be satisfied even if ADH is not.

 

[Matt0029]

Thanks but would an aav installed after the trap aid discharge on and also protect the trap as good if not better then a anti vac trap. As will alway a greater volume of air in as the water discharges?

 

[Ric2013]

I think it's much of a muchness. You can also get 'resealing' traps which contain no mechanical device to fail but do not run dry under suction.

 

[king of pipes]

You still haven't said what your connecting this waste to ?? Is it from a machine or machines of some sort or free running from sinks and the like

 

[Matt0029]

Just one machine, sorry.

 

[king of pipes]

personally I would run the waste in 50mm add a tee with a cleaning eye the machine would discharge via a washing machine standpipe with a 75mm water seal, have a continuous fall to drain keep it simple as possible in this instance a air admittance valve is not necessary. Regards kop