Cloakroom WC drainage plan

[Hugh Jaleak]

Worth looking at, appreciate with a small room you do want to maximise available space. Looking at the waste run in the drawing above, try and use swept bends as opposed to the elbows if you can. Easier to clean out should the need ever arise.

 

[swilli88]

Yes for sure would use sweeping bends, I just mocked up the sketch quickly for illustration!

I may even chase the brick wall 25mm to keep the room pretty much to same width.

what fall would you suggest for that basin waste run?

would you recommend an easy way to chase into brick without a expensive tool rental. Angle grinder with diamond blade and a cold chisel/light kango?

 

[Hugh Jaleak]

Fall, 1:40 should be fine.

Depends how hard the bricks/blocks are!

 

[swilli88]

great thanks.

I was looking at different fittings for connecting chrome pipe to plastic as it enter the wall and found this link...

https://mcalpineplumbing.com/plasti...3235a-cbc-90deg-bend-cp-brass-x-abs-connector

this looked perfect but i realised it said ABS on the plastic side. I believe the waste pipe i have is PVC. If looking at solvent welding do I need to ensure all the pipe is either ABS or PVC and they cannot weld together?

 

[swilli88]

@Hugh Jaleak @sircerebus666

so with this type of pan connector, often they are advertised as 'with VENT boss', which got me thinking. If I bring my basin waste to this connection is there likely to be siphoning issues when the toilet flushes which could pull on the basin trap? If so could i just add a 32mm tee somewhere between pan connector and basin waste with a 32mm AAV on it, just to serve as an anti siphon when the toilet flushes? Could be overthinking but I would really appreciate your input here

 

[Hugh Jaleak]

Details should be stamped on the pipe, solvent waste is usually ABS, although muPVC isn't unheard of. Apparently they are not supposed to be glued togther, although cant say I've ever tried to give an opinion.

Can drop a 32mm AAV in where required, I'm fairly confident the WC shouldn't pull the basin trap, but if you want belt and braces, for what the AAV costs, just fit one.

 

[swilli88]

@Hugh Jaleak

can the aav, if I fit one, be inside a stud wall? obviously less air flow in there but surely enough to be the little safety net the system set up might need?

i would probably choose to put it on a 32mm tee where the bottle trap enters the stud wall or where it leaves the wall to join to toilet pan connector

 

[Hugh Jaleak]

It wont hurt in there, but be mindful, if it jams open or otherwise fails, you may need to get to it to repair/replace. Ideally without punching a hole in the wall.

 

[swilli88]

Yes I will attempt to configure it in such a way that I need only remove a wood panel or two to access it in the event of repairs or failure, thanks

 

[swilli88]

this is more or less what i was imagining, and found an image so thought id post.

also something maybe like this if i need to do it a little bit further down the run for space reasons behind the basin itself

but I have a question about the height of the AAV. I found images like this

stating a min height from the tee of 4 inches or 10cm. Is this really necessary if my main reason for putting it in is to ensure the toilet flushing doesn't pull on the basin trap? once its above the level of the trap in the toilet im guessing im ok? Can any the wiser men confirm? @Hugh Jaleak

 

[swilli88]

excuse the very crude sketch, but this is what I meant by the last comment in my last post

ignore the lack of bends and accuracy. Basically if the only purpose of this AAV is to protect the basin trap from pulling when the toilet flushed then is it ok to put it near the pan connector as shown? the system just needs a soure or air between toilet and basin? I think this makes sense

 

[mrrusty]

Just as an aside, have you considered a little macerator? We had to fit one because couldn't get a fall on the 110 needed. Little sanitop up discharging ~ 6m through 32mm. We only use it for no1s and it's been great. takes the sink waste as well. I know peeps say avoid them, but I had little choice and am happy .... so far...

With your long horizontal run it might be an alternative?

 

[Hugh Jaleak]

AAV's should, technically, be fitted above the spillover level of the highest appliance, (usually the basin), but doesn't always happen. I'd try and give things a test without one to begin with, if there's an issue you can retrofit one afterwards?

A macerator is always a last resort, 110mm pipe is infinitely preferable if the space is available and a suitable fall can be achieved.

 

[swilli88]

@Hugh Jaleak yes i hear you. I know it should technically be above the spill level of the basin but is that assuming you are concerned about the basin water siphoning the basin trap? if you are only really concerned about the toilet siphoning the basin trap (i think in my situation that's the case?) then does it only need to be above the level of the toilet?

I only ask for clarity because, even if i dont attach any AAV now, I may put a tee in the line rather than a bend and just cap it off for potential retrofit of AAV later so I just need to know where I can put it.

thanks

And im also with you on the macerator. Last resort for me too. Apart from the bulk and the noise I just dont like the idea of having to pump the unmentionable through the walls and definitely dont want it to be a 'just a number one' toilet either or even have that in my mind when nature calls

 

[Hugh Jaleak]

I've always believed an AAV needs to be above the basin to keep it 'dry', i.e. if the pipework were to block, it could possibly be forced open with pressure of the water backing up, and make a mess. If you're happy to take the risk, it can be fitted where you like.