horizontal soil pipe trouble

[radrad]

I had a bedroom converted into a bathroom with sink and shower. Both have traps, connected to a 40mm waste pipe that runs under the floor practically horizontal with several 90 degree bends for 2 meters, then on a 1:30 incline and into a soil stack. I have two problems that happen only occasionally:
1) the shower drains very slowly
2) using the sink causes water (or at least soap bubbles) to come up from the shower drain

Before jumping to the conclusion that there's a clog, I should add that it can also happen soon after plunging the drain. So I'm not sure that there's a clog like a hair ball, but I'm wondering if it's possible that bubbles (from soap or just air) get trapped somewhere in the horizontal section and restrict the flow on one random use of the facilities and pop when the water flow stops and don't re-form the next time? If anyone has heard of this or have another idea, could you advise me how to fix it please? There's no easy way to get to those pipes now as they are under a tiled floor. I've tried plunging, pouring in unblocking liquids, nothing helps, it seems random. Many thanks!!

 

[motorbiking]

If you can't get to the pipes, there is not much you can do. If you decide its worth openning it up, then consider separate pipes for sink and shower to the soil pipe. I'm guessing they connect at some point close. Use shallow traps, so you can increase the fall of the waste water.

Make sure the sink connecting pipe is not on a T with the shower.

 

[Harry Bloomfield]

2) using the sink causes water (or at least soap bubbles) to come up from the shower drain

That is because the shower is much lower than the sink and both share a common single pipe out to where ever it discharges. The fix is to add a second separate drain to where ever the first one goes.

Another option, might be to add some sort of a one way valve into the shower pipe, to prevent the back flow, but I have no information on these.

 

[just pumps]

I I've tried plunging, pouring in unblocking liquids, nothing helps, it seems random. Many thanks!!

Please stop using unblocking liquid chemicals.

 

[Koolpc]

Might be worth trying one of these..

McAlpine Anti-Syphon Bottle Trap White 32mm - Screwfix

Order online at Screwfix.com. Constructed from high temperature polypropylene with compression outlets. Suitable for use with basins and sinks. Neutralises negative syphonic pressure and eliminates gurgling. Multi-fit compression outlet suits waste pipes to BS EN 1451-1-2000. FREE next day...

www.screwfix.com

 

[Notch7]

Please stop using unblocking liquid chemicals.

are they bad?

 

[just pumps]

are they bad?

Can be explosive if two chemicals are mixed which often happens if people try one brand then another if the first brand didnt do anything. Been cases of people trying to unblock kitchen sinks being scarred. Im not certain what may happen to horizontal plastic pipes either.

 

[radrad]

If you can't get to the pipes, there is not much you can do. If you decide its worth openning it up, then consider separate pipes for sink and shower to the soil pipe. I'm guessing they connect at some point close. Use shallow traps, so you can increase the fall of the waste water.

Make sure the sink connecting pipe is not on a T with the shower.

You're right, the sink and shower are connected in the horizontal run of the soil pipe, probably with a T. Is there a better connector to replace the T with? Would it help to install a non-return valve on the shower branch or are they not good enough? I can't run a second pipe, but i could move the connection to a short vertical run of the same 40mm pipe that is immediately after the horizontal run, if that would help.

 

[motorbiking]

You want the joints staggered and as far away from the traps as possible.

My GF mum mixed drain cleaner with bleach and nearly killed herself (apparently it makes chlorine gas).

 

[Harry Bloomfield]

My GF mum mixed drain cleaner with bleach and nearly killed herself (apparently it makes chlorine gas).

Correct - you should never mix any cleaner which suggests it contains chlorine, with any which contain bleach, or the result is a deadly yellow-green chlorine gas.