Shower waste not draining away but no blockage and good fall

[stiggy6767]

Hi and apologies if this is covered elsewhere.

I have a long ( unavoidable) 40mm waste running from my shower. The shower is fitted with a "high flow" waste connected to a flexi- hose then into 40mm standard waste pipe.

The whole waste is about 5 metres long and has adequate fall i.e about 25mm per metre. The shower is at right angles to the waste pipe but I have swept the bend by cutting the wall out and curving the flexi-hose nicely.

About 2 metres from the shower a basin tees into the waste and again after about another 2 metres a bath tees in then the whole lot dumps into a trap via a big rubber bung seal to the house sewer.

Heres the rub, sometimes the shower drains fine and fast (after much gurgling and after about 15 seconds) other times it doesn't drain fast enough and the shower tray fills.

I guess that there is air or back pressure in the system.

How do I solve this please?

 

[bellairaphon]

sounds like its having trouble venting. and maybe abit of self syphonage.

 

[stiggy6767]

sounds like its having trouble venting. and maybe abit of self syphonage.

Thanks mate but what do I do about i.e what do I buy to fix it?
Remember I am a spark not a plumber!

 

[adlplumbing]

buy an aav and repalace eblow with tee peice and job done

 

[rojaca]

shower waste too long for diameter (3m max, 45mm/m fall I aim for)
best run bath, shower and basin wastes in individual waste pipes
easiest step to put aav basin waste which will help it vent at branch. would at least separate bath and basin waste from shower.

 

[stiggy6767]

Hi and thanks for your replies really appreciated. Sorry but I'm being thick.
Firstly what is an aav?
Secondly where should I put this given the following layout.
Shower trap directly connected to flexi hose which sweeps 90 degrees and joins 40mm diameter waste with straight twistlock connector. Basin tees into waste about one metre along from this and drops from basin height to waste pipe height after exisitng cavity and elbowing down. waste pipe finally bends 90 degrees outside property and bath waste joints via same arrangement as basin but at a lower level. Finally waste elbows and drops vertically into a sealed (bung) joint with the pot sewer 100mm dia trap thingy!
Sorry but need specifics like where and how or should I pay plumber to sort?If so how much would you pay?

 

[Nige F]

There is Back Pressure between the traps on the waste and the trap with the big rubber bung .

You don`t want an AAV - you want an old fashioned "puff pipe" vented to air outside OR arrange to un-seal that rubber bung. .
If you can , temorarily remove the bung seal and see the difference.

 

[stiggy6767]

Hi Nige
Sound sensible even to a spark i.e the system is fully sealed so no way air can flow in or escape! By back pressure I assume you mean air wanting to get out. By puff pipe I assume you mean an openening i.e with no fancy valve or anything. One last question does in need to go at a particular height or can I just fit a T inline with the waste run after all the appliance but before the drains.
Thanks again.

P.S the bung will have to stay because the joint needs to be covered over later but I will remove it to test the theory tomorrow

 

[Nige F]

you got it sussed You can use some overflow pipe and a reducer in the T. the outlet needs to be to outside through the wall and above the level of the bath - because that would be the overspill level . you could terminate it like a overflow pipe from a WC cistern , or level with the brickwork, or with an elbow on it facing down . If it`s really difficult to run to outside wall you could even snake it into the roof and drop down through the soffit Just as long as it goes to outside air to avoid any smells

 

[stiggy6767]

Thanks Nige
I appreciate the time you have spent on this already but just to explain more fully. The waste from the shower, basin and the bath all exit outside (into my adjoining garage) immediately they leave the appliance at their respective heights and the basin and bath drop to tee into the waste "run" which actually starts at the shower tray and falls gradually over 4 plus metres length to the sewer.
So the waste run start at circa 150mm height and finishes at zero. The highest point of the whole system currently would be the elbow from the basin. So if I understand correctly I can either vent from that elbow ensuring that the opening is above the basin overflow say 100mm higher or I can tee into the main run and put a vent pipe in to finish at the same height i.e basin overflow height? Either way I would use a 40mm tee and then fit a reducer to overflow pipe diameter or use a piece of 40mm pipe, finally given that this pipe will be pointing vertical what do I fit on the end?

 

[Nige F]

...on the end - nothing , but it must be to outside the house/garage to vent the positive pressure ( that I think is causing the problem )so it needs to go through a wall to the outside .- You might be OK in the garage but I would still run to free air outside the building- just for the slight smell from it .

 

[sooey]

Why not just run it back to the soilpipe above the highest tee?

 

[stiggy6767]

Nige you're a star mate
Replaced the basin elbow with a tee then put one of those acess plugs in it with a few holes drilled in. Works a treat shower flows away with no build up at all now!
If you ever need any advice on electrical stuff or flat screen tellies and AV give me a shout that's my bag.
P.S bellairophon you're a smart arse!