Gurgling drain!

[Deleted member 307320]

Just tried my new bathroom for the first time, all great apart from the really loud gurgling that comes from the sink when I empty the bath!

I can feel air flow from the basin overflow when the bath is emptying, so should I assume that I need to add an air admitance valve to the waste pipe from either the bath or basin?

 

[Madrab]

Unfortunately that's a common faus pas, it may be down to the bath and basin on the same run and the waste pipe been pipe hasn't been increased in size and/or may be overly long.

Are you are feeling air coming out of the overflow or being sucked in, try holding a square of toilet paper over it. If it's the latter then you could try an anti vac trap on the basin.

 

[Deleted member 307320]

Thanks. It's all 40mm pipe and the basin is only about a metre from the soil stack, and the bath another metre from that

 

[Madrab]

Ideally a bath should be on it's own run given the velocity it can drain at. If not possible then the pipe should have at least been increased to a 50mm at the tee and anti vac traps used.

 

[Deleted member 307320]

Ideally a bath should be on it's own run given the velocity it can drain at. If not possible then the pipe should have at least been increased to a 50mm at the tee and anti vac traps used.

To be honest, I wasn't aware that 50mm waste was available!

How long has that been a thing? I've only ever known 40mm and 32mm!

 

[Hugh Jaleak]

50mm has been about since plastic Waste pipe became a thing. The sheds don't stock it, as it is rather more specialist, (Urinals etc).

 

[Deleted member 307320]

50mm has been about since plastic Waste pipe became a thing. The sheds don't stock it, as it is rather more specialist, (Urinals etc).

Interesting!

I only do domestic plumbing so guess it's more of a commercial thing!

 

[Madrab]

Interesting!

I only do domestic plumbing so guess it's more of a commercial thing!

Not really, it's just bigger, follows the same principles and works the same way. I put 50mm outflows into lots of small bathrooms to overcome drainage issues.

 

[Deleted member 307320]

Ideally a bath should be on it's own run given the velocity it can drain at. If not possible then the pipe should have at least been increased to a 50mm at the tee and anti vac traps used.

As I said, never seen 50mm in domestic use...

I'll just add an AAV to the basin waste and hopefully that will sort it all out!

 

[Madrab]

As I said, never seen 50mm in domestic use...

40mm would normally be fine on individual/dedicated runs etc but now there's a lot more going on in bathrooms with higher flowing mixed outlets, longer waste runs, stacks being capped with AAV's, drains not being vented properly, badly or poorly designed/diy waste runs installed etc therefore 40mm isn't as suitable as it used to be, hence more reason now to increase the waste pipes to the larger size.

 

[Hugh Jaleak]

AAV's should only ever be installed as part of a new drain run where their suitability has been assessed.

 

[Deleted member 307320]

 

[Deleted member 307320]

I'm guessing this isn't correct...

Basin waste connects into the top of that tee

 

[Madrab]

It's not exactly wrong but certainly not ideal, the bath emptying will almost definitely pull on the basin trap as the bath outflow will easily fill that 40mm pipe and will create a vacuum in the basin waste pipe as it drops vertically, using an anti vac trap may allow you to get around it.

 

[Deleted member 307320]

It's not exactly wrong but certainly not ideal, the bath emptying will almost definitely pull on the basin trap as the bath outflow will easily fill that 40mm pipe and will create a vacuum in the basin waste pipe as it drops vertically, using an anti vac trap may allow you to get around it.

Yeah, thinking it through now I think you're right!

Unfortunately it's far to late to re-plumb, and I need a trap which works with the offset McApline space saver that I've installed, but I don't know of any anti vac traps which will fit.

Reckon I can stick an additional tee on the waste from the basin and stick on an AAV?