Unique plumbing issue in a 300-400 year old house

[cloudsix]

Hey all,

I'm hoping someone might have some unique ideas for me.

The Issue

We live in a house built in the 1600s. The plumbing has obviously been added to over time.

Occasionally, we get a sewage smell from our kitchen sink (when the dishwasher first runs), our upstairs ensuite sink/show, and our upstairs main bedroom sink and/or bath.

The kitchen issue I can replicate, but the upstairs issue happens at random times and it sure is a strong smell.

The Setup

The house has no outside vent, and instead uses an AAV downstairs, slightly higher than the sink. It uses one AAV for all waste/pipes.

Solutions I've Tried

I've changed the AAV to a new one.

I've had a plumber round who has fitted inline 1-way valves to the pipe from the kitchen sink, and the pipe to the ensuite sink. We did have it on the pipe from the ensuite shower, but the water drained too slowly with the trapped air. The shower now has a mini AAV, but no 1-way trap.

It feels like the smell comes from the sink more than the shower.

The 1-way valves don't appear to have fixed the issue.

Because of the position of the plumbing, there's no clear route to get a vent fitted outside.

Appreciate any help, ideas, or advice you all may have.

 

[ShaunCorbs]

Open waste pipe stuffed with a rag ?

 

[cloudsix]

Open waste pipe stuffed with a rag ?

This is a direct pipe from the ensuite sink. I guess the shower used to go through it as well, but they'd separated it - probably to try and combat the smell issue!

This pipe has the 1-way valve fitted, and the smell doesn't emanate from this area, though I'm no plumber, so it could be causing some kind of issue.

 

[ShaunCorbs]

Will still smell best to get it capped you can temp do it with a rubber glove and a cable tie to see if it helps

 

[cloudsix]

Does anyone else have any further suggestions? Perhaps someone has a diagram of a typical plumbing system with no outside vent?

 

[Devisham]

Are their waste water traps with working water seals on all the localised drains in the property?

 

[cloudsix]

Are their waste water traps with working water seals on all the localised drains in the property?

In theory, yes. But clearly, they're not performing effectively.

I had a look at the one in the ensuite which is where the smell comes from most often. It's using a straight-through pedestal trap. Based on the reviews over on Screwfix, it's not meant to be great. I'm tempted to swap it out for an anti-siphon compact McAlpine trap.

 

[Basher]

I've had a similar experience with a 16th c cottage.
I responded to a post here about smells earlier this year:

There should be a vent open to atmosphere (outside the building!) somewhere in the drainage system, possibly even in an adjoining property. The reason is to relieve any occasional positive pressure in the system, and without this, smells can find their way by blowing past traps, or through a faulty Air Admittance Valve, or through any leaking joint, into the house. It's become the norm to install AAV's in new bathroom or toilet conversions, but they are only to allow air into the drainage system, to stop a vacuum forming from say a toilet flush, which could suck water out of a trap.

I bought one of these to track down the source of sewer gas. It can be a bit sensitive to set up/ adjust, but it did work!

 

[cloudsix]

I've had a similar experience with a 16th c cottage.
I responded to a post here about smells earlier this year:

There should be a vent open to atmosphere (outside the building!) somewhere in the drainage system, possibly even in an adjoining property. The reason is to relieve any occasional positive pressure in the system, and without this, smells can find their way by blowing past traps, or through a faulty Air Admittance Valve, or through any leaking joint, into the house. It's become the norm to install AAV's in new bathroom or toilet conversions, but they are only to allow air into the drainage system, to stop a vacuum forming from say a toilet flush, which could suck water out of a trap.

I bought one of these to track down the source of sewer gas. It can be a bit sensitive to set up/ adjust, but it did work!

I think the attachment failed to attach?

There is no vent to the outside. This is a super old, listed property, with nothing adjoining. The only pressure relief in the whole system is the one pictured, but it's below all appliances except the kitchen.

 

[Basher]

I think the attachment failed to attach?

There is no vent to the outside. This is a super old, listed property, with nothing adjoining. The only pressure relief in the whole system is the one pictured, but it's below all appliances except the kitchen.

That's odd about the link - it's showing up OK on my tablet!
The item was Described as:

Natural Techamor Y201 - Methane Propane Combustible Gas Leak Sniffer Detector with Sound Light Alarm - Portable Gas Sensor Tester​

We eventually solved our problem by installing an open vent on the system. Can you not create one externally? I was under the impression it was a Building Regs requirement, though these things can be difficult with listed buildings.

 

[cloudsix]

I think the external vent is the ideal solution, but with the walls being so thick, and the plumbing positioned where it is, there's no obvious route to getting outside!

Thanks, I'll have a look at what you're suggesting with the detector.

 

[Basher]

I think the external vent is the ideal solution, but with the walls being so thick, and the plumbing positioned where it is, there's no obvious route to getting outside!

I was thinking more of providing a vent to the underground soil pipe in the garden. Is there an access/manhole cover in the vicinity?

 

[cloudsix]

I was thinking more of providing a vent to the underground soil pipe in the garden. Is there an access/manhole cover in the vicinity?

Yes, there's one just outside of where the current AAV is in the house

 

[Basher]

Yes, there's one just outside of where the current AAV is in the house

Well, this might not be encouraged by the professionals, but it would be interesting to prop open the inspection cover a tiny bit, say 1cm, to vent any positive pressure, and see it that has any effect on the smell appearing indoors. Just short term as an experiment!

 

[cloudsix]

Well, this might not be encouraged by the professionals, but it would be interesting to prop open the inspection cover a tiny bit, say 1cm, to vent any positive pressure, and see it that has any effect on the smell appearing indoors. Just short term as an experiment!

Wouldn't the positive pressure need to come from behind the flow?

 

[Basher]

Wouldn't the positive pressure need to come from behind the flow?

The positive pressure I'm referring to comes from other users elsewhere on the system, or from a pumping station. If you are miles from other houses, and from underground equipment on the system, this is probably a red herring.

 

[cloudsix]

The positive pressure I'm referring to comes from other users elsewhere on the system, or from a pumping station. If you are miles from other houses, and from underground equipment on the system, this is probably a red herring.

Interesting!

One thing I noticed is the shower tray trap cover doesn't have a tight seal, so I've ordered a new one. Hoping it fits.

If that fails, I'll give the outside cover a nudge.

Appreciate your thoughts.

 

[Ric2013]

The open pipe stuffed with a rag is a smoking gun. If your drains aren't airtight, then that really is the most likely cause of sewer gasses coming into the house. No point having a load of traps and one-way valves if the pipe is left open (and blocked with a rag).

Until you've capped that pipe in an airtight manner (whether with a proper cap or a rubber glove/gaffer tape as has been suggested), looking for additional causes is likely to be only a waste of time and money.

 

[cloudsix]

The open pipe stuffed with a rag is a smoking gun. If your drains aren't airtight, then that really is the most likely cause of sewer gasses coming into the house. No point having a load of traps and one-way valves if the pipe is left open (and blocked with a rag).

Until you've capped that pipe in an airtight manner (whether with a proper cap or a rubber glove/gaffer tape as has been suggested), looking for additional causes is likely to be only a waste of time and money.

Are you suggesting that part not being airtight in the cellar could cause the smell from a different room 2 floors up?

 

[Ric2013]

Are you suggesting that part not being airtight in the cellar could cause the smell from a different room 2 floors up?

Good observation. And no, indeed unlikely. But it will stop you being able to carry out an air tightness test on the remainder of the system which would seem to have been what your plumbers should have done initially instead of changing traps and fitting valves at random.

If it passes a tightness test, then we can assume a trap. If it fails, you may just be able to find the leak with gas leak spray or similar. If it won't take a pressure at all, then there may be a 20mm hole drilled into the pipework - and yes, I've come across one!

 

[cloudsix]

Good observation. And no, indeed unlikely. But it will stop you being able to carry out an air tightness test on the remainder of the system which would seem to have been what your plumbers should have done initially instead of changing traps and fitting valves at random.

If it passes a tightness test, then we can assume a trap. If it fails, you may just be able to find the leak with gas leak spray or similar. If it won't take a pressure at all, then there may be a 20mm hole drilled into the pipework - and yes, I've come across one!

I agree it's definitely worth sealing, either way.

Tightness test sounds like a good starting point once I'm sure this shower trap is fitted properly. Just need to find one with a seal the correct size.