Do I need air inlet valves

[ricardo100671]

I this design and concerned toilet flush will pull out traps all traps. So thinking to add air inlets, at and, above sinks, but wonder how to deal with low level of shower and bath.

 

[MikeGrahamT21]

Mine is like that and have no issues. I have an AAV outside, so after all of the connections on its way to sewer

[Nickfromwales]

17 hours ago, ricardo100671 said:

I this design and concerned toilet flush will pull out traps all traps. So thinking to add air inlets, at and, above sinks, but wonder how to deal with low level of shower and bath.

 

 

Hi.

If the invert, the lowest point of the outlet of the WC and the lowest point of the horizontal foul pipe discharging to the sewers is less than 1300mm then you won’t have any issue whatsoever.

 

The only way water gets sucked out of traps is by the flush water etc dropping a full storey of a building, vertically, and then there is a vacuum created behind it due to velocity. That’s when you need an air admittance valve above it to compensate for / neutralise the vacuum.

 

Looking at your pic you have less than 1000mm invert(?) so the flushed water will simply not be travelling fast enough or for long enough a drop to create any vacuum.

 

The only problem I see is with the pipe rising to a kitchen sink which will defo need an air admittance valve at its highest point (and where it is accessible), and I would do that run in 50mm pipe and fit a 50mm AAV vs 40mm (due to food waste & solids etc). Be sure to use bends not elbows on that pipework run too, so that run can be retrospectively ‘rodded’ with ease if a blockage ever occurs. Is that run more than 3000mm?

 

[ricardo100671]

Thanks Nick, for the perfect explanation. Exactly the assurance I needed since this will all be burried so didn't want to do something I would regret.
All pipework is either 110 or 50 and the kitchen run is around 2m (excl. Upstand)

[Nickfromwales]

36 minutes ago, ricardo100671 said:

Thanks Nick, for the perfect explanation. Exactly the assurance I needed since this will all be burried so didn't want to do something I would regret.
All pipework is either 110 or 50 and the kitchen run is around 2m (excl. Upstand)

Great, no probs  

For any of the runs off 110mm I would defo use 50mm until at the room or appliance, and then reduce down when it is above ground / in wall / exposed etc where you can then get to it. I never bury 40/32mm pipework, unless its the very short bit under a shower trap and that's a factory fitting which won't take 50mm directly.

 

Use solvent weld PVC vs push-fit too, as they aren't reliable IMHO.

 

If the kitchen sink drops less than 1300mm before going horizontally to the second drop, then to 110, then you'll probably not need an AAV at the kitchen sink, but I think I'd put one in for Justin (Justin Case)  to be belt & braces. If you've an appliance (dishwasher or washing machine)  in the kitchen then don't connect via the sink trap appliance connector as that's noisy to the room when pumping out. Fit an appliance upstand instead, tee'd into the kitchen sink waste pipework eg after the sink trap. Much better job.

 

https://www.screwfix.com/p/floplast-washing-machine-trap-white-40mm/18640?tc=ET2&gad_source=1&gclid=Cj0KCQiA7se8BhCAARIsAKnF3rwrmETQqq319b3N-BPY_d3gqzuT1HRwstHyu0gi6IZk5EPTp69VC6kaAvObEALw_wcB&gclsrc=aw.ds

 

One for each appliance.  

[Alan Ambrose]

>>> Use solvent weld PVC vs push-fit too, as they aren't reliable IMHO.

 

For us beginners - is that ‘don’t use’ or ‘are reliable’?

 

p.s. really appreciate the detailed explanation and recommendations.

Edited January 24 by Alan Ambrose

[Nickfromwales]

Push fit waste fittings are the last thing I’d use. 
 

Solvent weld is bombproof.

 

Try a few test joints with solvent weld, as it goes off in seconds and offers no room for ‘tweaking’ , eg if you’re a novice and have not done this type of plumbing work before. 

[MJNewton]

Just now, Nickfromwales said:

Push fit waste fittings are the last thing I’d use. 
 

Solvent weld is bombproof.

 

Are compression fittings (decent ones from, say, McAlpine) a good happy medium? I am thinking in terms of being both watertight but still dismantleable(sp?) ...

[Nickfromwales]

17 minutes ago, MJNewton said:

 

Are compression fittings (decent ones from, say, McAlpine) a good happy medium? I am thinking in terms of being both watertight but still dismantleable(sp?) ...

Compression stuff is very good tbh. Fire away. 
Just have a reality check about where these go and if you’re ever going to actually dismantle them, ever, and if not then go for solvent weld (permanent) there and only fit compression where you think it’s a possibility that you’ll need to fettle retrospectively. 

 

 

Note:

 

Pushfit fittings will not go onto solvent weld pipe and vice versa.

Compression fittings will fit onto both pipe types. 

[MJNewton]

3 minutes ago, Nickfromwales said:

Compression stuff is very good tbh. Fire away. 
Just have a reality check about where these go and if you’re ever going to actually dismantle them, ever, and if not then go for solvent weld (permanent) there and only fit compression where you think it’s a possibility that you’ll need to fettle retrospectively. 

 

 

Sounds reasonable, particularly the reality check as to whether a joint *really* is likely to ever need to come apart and, even if it might, whether chopping out a permanently attached fitting will suffice. I suppose compression fittings are pretty bulky too which might have relevance in some situations. 

Edited January 24 by MJNewton

[Nickfromwales]

1 minute ago, MJNewton said:

 

Sounds reasonable, particularly the reality check as to whether a joint *really* is likely to ever need to come apart and, even if it might, whether chopping out a permanently attached fitting will suffice. I suppose compression fittings are pretty bulky too which might have relevance in some situations. 

Cost for one, ugly as shit for another, lol.