Water backing up

[Gilesda]

Hi all.
My shower tray waste started to back up a few weeks ago. It reached the point where I had to turn the water off mid shower and wait a couple of minutes for it to drop.

There was no apparent blockage close to the tray and running a 8mm dia drain snake through it went all the way through to the stack with no resistance.

I bought a £10 endoscope camera off Amazon and attached it to the front of the snake. Running it through the pipes to the stack the pipes barely had a stain on them. I was amazed the camera worked so well actually.
The shower tray outlet is less than 2m from the stack. It's 40mm pipe all the way through. The fall from the shower outlet is about 120mm over the pipe length.

A basin is next to the shower and releasing water from that, the water appears in the shower pot.
At the end of the run close to the stack is a toilet. Flushing the toilet results in gurgling at the shower waste. The toilet empties into the stack above the shower and basin waste pipe. The picture shows how it is laid out.
That stack is a stub stack about 900mm high which is sealed at the top. Could a lack of air in the stack cause the shower to go away slowly? It's worked ok for two years, though putting the shower on a very high setting it would back up when first installed. Now it backs up regardless after being in use for a few minutes. I'm trying to work out my best and easiest option. Any ideas are most welcome.

 

[CBW]

Is any other part of the sewer vented? Eg neighbours?

 

[Gilesda]

Yeah the house has a two storey stack that is ventilated. This main stack is about 3m from the downstairs shower room stack.

 

[CBW]

Then I wouldn’t have thought a stub stack lacking in ventilation when the main is ventilated, would cause the issues you describe. I suspect a full/partial blockage, be it in the stack or main drain.

 

[Harry Bloomfield]

Is there a manhole inspection close to the base of the stack, which you could take a look in?

 

[Deleted member 292770]

You say youve had the camera right out to the end of the pipe , but just make sure that the 40mm pipe isnt overshooting the boss and catching toilet paper and waste inside the stack.

 

[Gilesda]

I ran the camera to the stack there was no blockages just white pipe with a bit of staining. The camera went into the stack, it was easy to tell by the increase in diameter. I pulled the camera back a bit and flushed the toilet. I could see the toilet water flowing down the stack. The end of the 40mm pipe hadn't gone into the stack.

I stopped typing there and went out to check a manhole. It's piddling down with rain here but it only took a second. This house is an early seventies build and has an interceptor which used to block at least once a year. It's easy to clear it, it blocks in the trap that interceptors have built into them. I used to snap a branch off a tree we have and a few pokes it clears. I haven't checked it for a while till just now and it's blocked again. So it looks like there is no ventilation to the shower room stack. So I'm guessing that's the problem. That's a job for tomorrow.