[sapper1]

I have a down stairs toilet connected to waste as usual. In addition there is a hand basin whose waste is connected via a P trap to the same waste pipe. Lately the water level in the toilet bowl falls allowing gas from the drains to enter the room. I have noticed that the water level in the bowl is oscillating after flushing. I propose to replace the P trap with an anti vac type. Is this the right thing to do? Thank you

[massplumber2008]

Hi Sapper

If this is something that didn't happen until just now then replacing the trap is probably not going to resolve the issue... ;)

More likely here is that the toilet is partially clogged and siphoning the toilet water out, or the toilet/hand basin vent may be clogged.

I'd check this stuff before replacing any parts!

Back to you...

Mark

[hkstroud]

Not likely. If water is being siphoned out of the toilet bowl it is most likely because you have a blocked vent stack. Never heard of an anti vac P trap.

[speedball1]

More details please! Does the bowl filln bup and slowly drain away. Is the level low from the git-go? Have you checked the little tube running from theballcock to the overflow tube? ( That's the one that fills the bowl. )

I have noticed that the water level in the bowl is oscillating after flushing

Please explain what you mean. Describe this "oscillating". Back to you, Tom

[sapper1]

Thanks to all who replied to me.
I believe the problem is resolved. I fitted the anti-vac P trap (available from Pochin) and the water level is now stable, at the correct level and is not oscillating after a flush. I have also used two buckets of water poured slowly into the loo and all appears well. Thanks so much chaps...

[speedball1]

We thank you for the update. If we can help in the future please calln on us. Regards, n bnTom

[ballengerb1]

This sounds like what is know here as a AAV air admittance valve. It made this issue go awy for now but the real problem is still there, most likely a clogged vent stack like Harold mentioned. Do not know what Pochin is but suspect you are not located in the USA, where are you living please

[massplumber2008]

Like Harold and MARK mentioned, Bob... :p

[ballengerb1]

I just wanted to get the true name for the AAV out there because anti vac P trap is not part of our vocab. Also reenforcing that the guys are correct. Me, I'd be fishing out that stack if I could avoid falling off my 12/12 roof.