Constant toilet blockage - insufficient fall from toilet to vertical soil pipe?

[HerrB]

Hi, any advice highly appreciated here please as I've already spent GBP1600 and still not had my plumbing issue resolved. In short, I live on the 3rd floor of an Victorian conversion and experiencing constant toilet blockages. Plumber came over and said it looks like there's not enough fall from toilet seat to main vertical soil pipe which runs down the outside wall to the basement. There is around 6 metres of distance from toilet to main vertical soil pipe and we think there's about 15cm of fall (which I believe is the minimum required for successful flow). The plumber is suggesting we put up scaffolding to lift the pipe from the exterior to investigate but i'm worried that after spending 2k on scaffolding the answer will be "sorry, we can't raise the pipe enough". What I find hard to believe though is prior owner lived in this flat for nearly 10years and can't possibly have done so without a functioning toilet. Is there anything else we can do? I've heard a Saniflo/pump toilet is a possibility but you can't have one if this is the only toilet in your flat. Thanks in advance

 

[Paulus]

Your plumber is right in what he says but before spending the money on scaffolding you should get him to assess the possibility of improving the fall on the pipe. There is no point spending that kind of money if the problem can't be rectified.

The only other alternative would be a saniflo.

 

[Simon F]

welcome to the forum.
what have you already had done for£1600!??
what gets put down the wc??
is it only your toilet affected, or others downstairs?
is the stack pipe open vented or does it have an air admittance valve? that is not working??
fitting an additional aav due to pipe length might help

 

[Reg Man]

6 metres is the maximum allowable length for a single W.C and you are required to have a fall of 18mm for every 1 metre length of pipe. 108mm from W.C to soil stack. If its to steep or to shallow it can leave the solids behind.

 

[HerrB]

Thanks all for swift reply. Here's what has already been done (total cost 1600GBP), it feels like its cost this much just to diagnose the problem, which leads me to question expertise of the plumber in question. They are still unable to offer me a definitive solution....

" soil pipe blocked and caused water to back up through basin toilet and bath. Too high to use ladders to remove soil from outside wall and rod would need scaffholding. Alternative method is to remove toilet and rod maybe with hep pipe as awkward angle" .

" removed toilet and used hep pipe down soil run to clear blockage, still does not flush correct. I feel there is no fall to the soil pipe causing to backup and leak." the plumber inspects the main drain ( inspectable form garden of lower ground flat) and sees it is badly blocked.

The manager of the company comes the following morning (29-08) to assess problem. He suggests a CCTV scan of piping system to fing blockage. 2 plumber come in the afternoon to carry out the CCTV survey to 4" horizontal pipe under floor. Found blockage at 90* bend. Rodded clear. Toilet flushing okmat this point however plumber says pipe still needs more of a fall.

The day after, after the toiled was remounted, there was a small leak at pan connector. Plumber came back and replaced it.

Works done on 3/09.Works involved lifting carpet and floor in hallway to raise the 4" waste pipe by approx half inch with strap band internal.

After all this, we still have a problem. The plumber in question has been to visit 5 times and still can't tell me for sure whether or not I can get enough fall on the pipe. Feels like I keep writing cheques for nothing, just for a diagnosis, which I don't even have yet.

Any thoughts on what are the cheapest way forward with highest chance of success? It's only waste that goes down this toilet, the stack pipe is vented but it has been suggested not sufficiently so, and this affects only my flat (I'm on the top/3rd floor).

 

[Ray Stafford]

You say that the previous owner was there for 10 years. Has the WC been changed since then?

I am just wondering if the fall on the soil pipe - which might have been just the right side of marginal with the older WCs with 9lts cisterns, may have been pushed to the wrong side of marginal by a new WC with a 6ltr or even 4ltr flush?

 

[rpm]

You are correct when you say that a macerator cannot be the only toilet (but people do it!).

I like Rays idea re 6 or 9ltr cistern.

 

[HerrB]

thank you very much for your comments much appreciated. The toilet was actually renovated around 1yr ago so the cistern thing could well be the issue! Can I get a 9litre put back in (I understand regs are 6ltr max nowadays)? Failing that is there such a thing as a powerful flush toilet nowadays? maybe i can install one and get things moving down that pipe with a bit more speed! thanks again to you all

 

[Ray Stafford]

Some older style WC designs still use a 9 litre shell, and its the fittings inside that are limiting the flush to 6 ltrs. It wouldn't take much for an experienced plumber with the right bits to restore it to 9 litres.

Not that I am recommending that, which would clearly be outside current regs, and therefore a VERY BAD THING.

 

[rpm]

6 metres is the maximum allowable length for a single W.C and you are required to have a fall of 18mm for every 1 metre length of pipe. 108mm from W.C to soil stack. If its to steep or to shallow it can leave the solids behind.

Pipe fall to shallow I can understand but why a problem if pipe fall is to steep?
Thanks in advance.

 

[Centralheatking]

Hi HerrB you will find that drain problems are quite popular and you will get plenty of advice
from us inc me (love drain probs) can you post some pics and maybe a diagram -
not a special diagram just a sketch - then we can all see what this all about - Rays idea
is good ......... centralheatking

thank you very much for your comments much appreciated. The toilet was actually renovated around 1yr ago so the cistern thing could well be the issue! Can I get a 9litre put back in (I understand regs are 6ltr max nowadays)? Failing that is there such a thing as a powerful flush toilet nowadays? maybe i can install one and get things moving down that pipe with a bit more speed! thanks again to you all

 

[mutley racers]

Solids stay behind as liquids fall too fast

 

[AWheating]

Pipe fall to shallow I can understand but why a problem if pipe fall is to steep?
Thanks in advance.

as mutley has stated, to greater fall can lead to the water running away to fast leaving the solids behind. Especially a problem on longer runs.

 

[rpm]

Mutley & AWheating,
Thanks guys, get it now.

 

[snowhead]

You've still got a partial blockage in the pipe to the stack.
HEP pipe is not the best solution for rodding.
Get a decent drain clearing company in, most of whom have a selection of rodding equipment both electrically powered and manual.You'll still have to pay a plumber to remove and refit the pan tho'


Something like this (from USA site but still used here);

Drain Cleaning Equipment-Sewer Snakes and other Drain Machines and Tools

 

[rpm]

6 metres is the maximum allowable length for a single W.C and you are required to have a fall of 18mm for every 1 metre length of pipe. 108mm from W.C to soil stack. If its to steep or to shallow it can leave the solids behind.

I`ve got a similar problem with a Sanicubic pump so am I reading this right? The pipe from the wc should fall around 18mm per metre - yes? But I don`t understand where the 108mm figure comes from.

 

[mutley racers]

18×6 metres

 

[rpm]

18×6 metres

:mad2:

 

[stevetheplumber]

a fall of 150 over the 6mm length sounds ok to me get the bit about holding it up with banding suggests there was a dip in it at some point i would get it jetted

 

[Reg Man]

Is this a straight 6 metre run to the vertical soil stack?

 

[HerrB]

View attachment SoilPipe.pdf I had a go and drawing a diagram of the issue, apologies for the terrible drawing but I always struggled in art class...

 

[Centralheatking]

Its a fine drawing - well done HerrB - CHK we will have more clus now CHK

 

[Reg Man]

No open vents or AAR valves. That won't help.

 

[Centralheatking]

I agree with Reg Man the system appears to not vented - maybe a dirgo ie non rtn
air valve might help - but how this stands with building regs not sure CHKing

No open vents or AAR valves. That won't help.

 

[stevetheplumber]

yes its probably airlocking as theres no air getting in behind the water plug even a 50mmm durgo after the pan would probably cure the problem idealy the four inch should go to atmosphere after the pan

 

[phil the bucket]

Is it an old syponic toliet as prop can arise when the wrong sypon is fitted (need to keep the ball inside )
Has the sypon been changed does it look new .

bit strange how it's been working for 10 yrs then suddenly starts to block especially on the top floor of a high building is there prob in the floor below ?