Correct fitting for soil stack under floor

[Daniel Banche]

This photo shows the top of the soil stack, as it was installed by the house's previous owner, under the floorboards of the en-suite bathoom on the 1st floor of a standard detached house.

As shown, there is a shower trap (the shower tray removed for the moment), and also there is a waste connection from the washbasin going into the soil stack. The large pipe going to the right leads to the toilet, which is just out of the photo.

Originally, I know the soil stack used to go up through the floor and into the loft and out of the roof (as usual). The previous owner didn't like the space that took up, and sealed the soil stack under the en-suite floor with what I have discovered is a 110mm air test plug bung, on which the rubber has cracked and doesn't stick in the hole anymore.

My question is this - is this a valid way of sealing the soil stack? I thought that at least it needed a vent. I want to know before I just go and buy a new replacement bung of the same type.

Since we moved in, the en-suite has always smelt bad, and we suspected that the smell came from the shower trap. The washbasin never showed any signs of its trap being emptied during a toilet flush, but I suspect that the shower trap is shallower and may have been emptied by the vacuum.

Should I just use another bung, then buy a trap on the shower which can handle the vacuum?

 

[rpm]

Excellent first post Daniel, clearly written with a good photo, I`m sure somebody will be along to help you soon but it`s not my sort of stuff to comment on. Welcome to the forum.

 

[SimonG]

First thing is measure the depth of them joists. Dont like the look of that notch.

On the drain front, no its not a valid method of terminating the stack. Depends what you need to be doing in there. Ideally extend pipe up over and fit air admittance valve. Or try anti syphon trap on washbasin.

 

[solutions]

No Daniel that is far from correct. Is there another stack in the house that is vented through the roof?
Idealy a vent should be reinstated perhaps from the branch to the toilet as the original stack is clearly now blocked by the location of the shower tray. You could remove the branch and swap it for a bend or insert a short section of 110 in to the top of the branch and seal that with an access cap. But sealing the stack with out providing a vent on the same stack will only serve to continue to cause problems with the connected traps and possibly with your toilet flushing. A stub stack with an aav may resolve your traps being sucked but i prefer to provide a proper vent. There needs to be a means for the air in the pipe ahead of the water running to waste moving away without pushing out of other connected traps and equally air needs to be able to be drawn in behind flushed water to prevent a vacuum forming and sucking water from other connected traps. It is possible to reduce the diameter of the waste pipe that vents to the roof if it will be easier to route it I believe 70 mm is the minimum or it could be 75 I cant recall. I have in the past run 3 40mm pipes back to the soil branch then up inside a stud wall to reach the loft where they were connected back up to the original 110 through roof vent.

 

[rpm]

Did notice the notch SimonG but wasn`t sure if it was just a support for the pipe, thought a joist went wall to wall but then I`m still learning.

 

[solutions]

First thing is measure the depth of them joists. Dont like the look of that notch.

On the drain front, no its not a valid method of terminating the stack. Depends what you need to be doing in there. Ideally extend pipe up over and fit air admittance valve. Or try anti syphon trap on washbasin.

Good spot Simon that notch is definitely not allowed. too close to the supporting wall and too deep for the depth of that joist.

 

[Daniel Banche]

Thanks for all the replies. I'll read though properly when I have time and come back with more detail.

Regarding the notch - is it the one on he left (on top) or to the right (on bottom)? The pipe in the notch on the right leads to nothing - it is the original route from he washbasin which was cut and blocked off by the previous owner.

 

[solutions]

Thanks for all the replies. I'll read though properly when I have time and come back with more detail.

Regarding the notch - is it the one on he left (on top) or to the right (on bottom)? The pipe in the notch on the right leads to nothing - it is the original route from he washbasin which was cut and blocked off by the previous owner.

bottom left is worst but neither are right. They cut out to mutch of the joist and are in the wrong part of the joist. which means the joists are now much weaker. I would remove the pipework passing through the joists and investigate what would need to be done to strengthen the weakened joists. I dont know myself so perhaps someone on here can recommend hiw best to reinforce the damaged sections of joist or perhaps contact a structural engineer. I hope there is no bath on those joists, a full bath is a hell of a lot of weight.

 

[lame plumber]

if there was a bath it aint fallen through yet, sometimes we worry to much, after all theres a built in safety factor in all these calcs to cover for idiots with saws

 

[chris watkins]

if there was a bath it aint fallen through yet, sometimes we worry to much, after all theres a built in safety factor in all these calcs to cover for idiots with saws

The trouble is lame, yes there are safety margins but when is a notch too deep & when will it be OK? You can't test every one by filling a bath full of water & seeing if it goes through the floor now can you. :builder:

 

[lame plumber]

just using a bit of common sense here especially as a shower tray is at one end and a loo next to it. if its been there for an age it aint likely to go anywhere now. However I'm not advocating large notches etc but 80% of bathrooms you look at have been carved up and not one customer is going to say yes off you go and replace all those joists that havent failed to date.

 

[mache]

Joist notches clearly not to reg's but to be honest looks like there is supporting beam or block wall in the middle that they are bearing on. Given that I doubt if anything untoward is going to happen unless a dramatic increase in floor loading is applied.

 

[SimonG]

Like a bath?

 

[lame plumber]

Like a bath?

naw having a shower later, not that its any of your business

 

[solutions]

Have seen worse. Joists had been chopped to just under half depth down the center of the room to fit a 40mm waste (which of course had no fall) the run was about 2 meters long. The floor was like a trampoline. To make matters worse it was in a victorian terrace the joists were shallow and the bathroom was above the kitchen which stuck out from the back of the house in to the garden with a window looking out on to an alley which ran down to where the garden became full width. The kitchen had a door in to the alley, the customer was having the door changed for upvc only the fitters didnt realise that the top of the timber door frame was also the timber lintel holding the joists of the bathroom above. They took it out put in there new upvc door and frame and couldnt work out once they opened the door why they couldnt close it again. Top of the frame was bent like a banana by the weight of the floor above and there was no suite in yet. I informed the company I was subbing for and told them there was no way the customer could have her imitation cast iron freestanding bath, and they needed to get a structural engineer in before someone got seriously hurt.

 

[Centralheatking]

Thats a supporting wall under the notched joist so dont worry, it not ideal but not a problem. Altering all that pipework will be a nightmare. I would fit a vented trap to shower tray and make sure the basin one works. Put a new bung in or I think there is an insert for the top of the branch. Centralheatking

This photo shows the top of the soil stack, as it was installed by the house's previous owner, under the floorboards of the en-suite bathoom on the 1st floor of a standard detached house.

As shown, there is a shower trap (the shower tray removed for the moment), and also there is a waste connection from the washbasin going into the soil stack. The large pipe going to the right leads to the toilet, which is just out of the photo.

Originally, I know the soil stack used to go up through the floor and into the loft and out of the roof (as usual). The previous owner didn't like the space that took up, and sealed the soil stack under the en-suite floor with what I have discovered is a 110mm air test plug bung, on which the rubber has cracked and doesn't stick in the hole anymore.

My question is this - is this a valid way of sealing the soil stack? I thought that at least it needed a vent. I want to know before I just go and buy a new replacement bung of the same type.

Since we moved in, the en-suite has always smelt bad, and we suspected that the smell came from the shower trap. The washbasin never showed any signs of its trap being emptied during a toilet flush, but I suspect that the shower trap is shallower and may have been emptied by the vacuum.

Should I just use another bung, then buy a trap on the shower which can handle the vacuum?


View attachment 19006

 

[chris watkins]

Thats a supporting wall under the notched joist so dont worry, it not ideal but not a problem. Altering all that pipework will be a nightmare. I would fit a vented trap to shower tray and make sure the basin one works. Put a new bung in or I think there is an insert for the top of the branch. Centralheatking

I thought a "vented trap" kind of defeated the object doesn't it ??

There seems to be a lot of advice flying around here & most of it seems to suggest that you should leave that lot in place, it does not comply with Building Regulations & as per post 4 we would need to see where there is another vent pipe on the run & if that is the head of the run.

Your system needs sorting out by a pro, I would strongly suggest that you get it sorted out properly once & for all.
There are nearly always ways around drainage / vent problems without the need to replace the vent pipe directly above the branch, it is very unlikely to work correctly until it is.

 

[kris]

Defo best to be vented externally. The notch isnt the right way but i agree with chkg its right above partition so not end of world .can easily be strengthened. Like i said in previous post renew as much as poss with connecting onto existing vent terminal .(if it still exits)

 

[Daniel Banche]

OK, many thanks again for all the replies. I'm going to get someone else to look at it who I know has worked on the same houses too.

Regarding the joists - they are 21cm deep. That is indeed a supporting wall between the shower trap and soil stack. The shower tray edge (when I put it back) will be more or less above that notch on the left. I'm honestly not that concerned about the notch - it was there when the house was built in 1976, as far as I know.

The shower tray won't therefore be above the top of the soil stack. Originally, the soil stack continued up the floor and into the loft, which meant there was a large obstacle for the shower door (which was probably just a curtain in '76). This would have prompted the previous owner to make the modification to the soil stack.

The other consideration, is that while it would be ideal to have the soil stack routed to the outside wall (or at least some kind of branch vent), there isn't that much space between the outside wall and our neighbour's garage, just a small alleyway. An alleyway so narrow, that the wall insulation company refused to do the cavity wall insulation without scaffolding as a ladder would be too steep. My thinking is the inconvenient access to the external wall (considering this is on the 1st floor) is what stopped the previous owner (a heating engineer by trade I should add) from venting it outside.

On the other side of the wall behind the shower (to the far left out of photo) there is a built-in wardrobe. A solution, I think, may be to run a pipe from the soil stack under the floor into the space just under the wardrobe, then run it up vertically into the loft, within the wardrobe (boxed-in and enclosed of course) and join it back to the original vent in the loft. This keeps it hidden and still provides a vent.

 

[chris watkins]

Why doesn't the heating engineer bit surprise me !!!!!
Sounds a good plan to me Daniel, the vent up to outside (dry part) can be reduced to 3" (75-82mm) according to Building Reg Part H but at a push it could be reduced to 2" (50mm) & it would work fine.
Take the opportunity to sort out wastes if you can, I don't like two 40mm into one.

Good luck.

 

[solutions]

Why doesn't the heating engineer bit surprise me !!!!!
Sounds a good plan to me Daniel, the vent up to outside (dry part) can be reduced to 3" (75-82mm) according to Building Reg Part H but at a push it could be reduced to 2" (50mm) & it would work fine.
Take the opportunity to sort out wastes if you can, I don't like two 40mm into one.

Good luck.

your right 3 32mm would be better.
why the dislike of multiple pipes? I appreciate that as far as I am aware it is not catered for in the regs but should function all the same so long as no one tries to convert the loft and plumb a toilet in to the remaining vent. Ridge tile vents do essentially the same thing by changing the profile of the vent but supplying the same free vent area.

 

[chris watkins]

your right 3 32mm would be better.
why the dislike of multiple pipes? I appreciate that as far as I am aware it is not catered for in the regs but should function all the same so long as no one tries to convert the loft and plumb a toilet in to the remaining vent. Ridge tile vents do essentially the same thing by changing the profile of the vent but supplying the same free vent area.

Ooop's upset all the heating engineers on here again (not intended I assure you). I agree to a certain extent solutions but there has to be a limit. Would 10 x 10mm pipes be OK?
There is a difference between a single & multiples & that is the amount of friction proportionate to the surface area, along with the risk of blockage.

 

[solutions]

Ooop's upset all the heating engineers on here again (not intended I assure you). I agree to a certain extent solutions but there has to be a limit. Would 10 x 10mm pipes be OK?
There is a difference between a single & multiples & that is the amount of friction proportionate to the surface area, along with the risk of blockage.

You are not wrong. indeed I would only use such a means if it were absolutely necessary which it rarely is and then only of course on a vent portion of a stack. don't worry certainly not upset by you offering your sound advice.

 

[Centralheatking]

Centralheatking and his fellas are pragmatic and practical

New build has to be perfect thats why the QS/Architect/ etc
get paid so much.

However regarding existing buildings - of what ever age - and
when one regards the customers financial position - as long as
drains and water are left safe in our opinion that how we roll.

10x fellas x 40 years practical experience = alot in my opinion

And in case you doubt us we have done loads of medical gas, in hospitals (vac and O2) hydrogen and other rare gas in labs,

Big George (dead) and Jimbo did some submarines at
Cammel Laird and Bae at Barrow

We only really toy now CHK
Cenralheatking

 

[AWheating]

most new builds i see are far from perfect. In fact you would be mad to buy many of them sadly.