New Toilet Taking Ages to Drain - Trapped Air?

[Gigagator]

Hi all,

We've recently moved into a house that we've been renovating since the start of the year.
I've done a lot of work myself including fitting out the downstairs cloakroom with a new basin, toilet, cistern etc.

Everything has been running great until middle of the week when the downstairs toilet started to drain very slowly and gurgling when the water gets to the bottom of the pan.

It's been draining slower and slower over the course of the last few days and it's rather annoying.

It's a mid 1960's semi detached and the soil pipe is a clay pipe in the floor.
I am willing to say that the toilet and the run of pipe heading out to the street is not blocked.
We don't flush wipes or anything like that and honestly the toilet has been barely used since we moved in about three weeks ago.

I am wondering if there is some issue with air being trapped as there is no air admittance valve here, just a flexi pan connector that goes into the soil pipe in the floor.
Here are a couple of photos that show how the toilet is plumbed in:


Also a video here showing what is happening when flushing:
https://1drv.ms/v/c/99113be6c17538e8/ESAMcTGwyTZDgr85JEUkdl8Bcm1XBm-raqByaMpxT6vJzw?e=yaHOrU

To those of you with more experience with this sort of thing than me (it's the first toilet I've ever fitted), does this look like it could be trapped air, and an air admittance valve introduced would solve the issue?

The problem I have is the fall from the pan to the waste in the floor is decent with the setup as it is now.
If I introduce something like this

with an air admittance valve on the top (if this even all fits at the back), I'm not sure the fall on the waste will be sufficient, if present at all.

What are your thoughts on the above?

 

[denso13]

Looks like a partial blockage, trapped air is a non starter.

 

[Gigagator]

Looks like a partial blockage, trapped air is a non starter.

Why do you say that?
I am convinced it's not blocked as we've hardly used it. You are far more experienced than me though.

My next question then is where do I start with trying to clear a blockage? How do you find out what part of the run the blockage might be in?
Sounds daft but in 32 years on this planet I've not once had to clear a toilet blockage.

I have some fierce drain cleaner I can get from work (a high school) that is quite nasty stuff and emits smoke when you pour it down a blocked drain - would that be worth a try?

 

[Nige F]

Don't use the drain cleaner ! is there a manhole outside ?

 

[Gigagator]

Don't use the drain cleaner ! is there a manhole outside ?

Yes there is. Three of them actually running right the way up the driveway.
Me and my father in law lifted all of them about a fortnight ago just to check their condition and they were spotless. Chucked a few buckets of water down them and they were running lovely, could eat your dinner off them.... Well, not quite.

I might go and pry one up quickly now and have a look.

 

[foxhole]

Do you have small children? Has someone flushed building materials down it? Is there and external stack .

 

[Tricky-Dicky]

Looks much like a partial blocked sewer pipe.
Lift all manhole covers,
Flush the toilet - helper needed, use a piece of toilet tissue for identity,
Look at the flow in each manhole,
Hopefully you will detect the problem,
or at least find the manhole that the toilet drains into,
then rod that particular pipework.
Hopefully this helps.

 

[HERTS P&D]

Blocked manhole, check and report back.

Andy

 

[Hugh Jaleak]

I've spent 35 years working in and around drains. You have a blockage.

Air Admittance Valve wont solve anything, as the title suggests, it will let air in, not out. When you flush the the water cannot get away, as the pipe is full downstream, and in order for the pan to empty, it needs to displace the air in the pipe trapped between the pan and the blockage, you're probably quite fortunate the flexi pan connector hasn't popped out the floor to be honest.

I would seriously consider changing that Flexi, especially on a ground floor WC. They are not spectacularly strong, and being translucent, Rats can be attracted to a source of light. The flimsy plastic is no challenge for a Rat, and you may find they'll have chewed straight through it in next to no time, and have a front door straight into your House....

As for the WC, You may not have used it much, but you also have no idea what's been put down there previously! Secondly, it may not be that actual run that is blocked, the issue could be much further downstream, the system has backed right up, which is leading to the issue you are experiencing. An upstairs WC may still go into the same pipework, but wont display any symptoms due to the setup.

Check outside, and on neighbouring properties if needs be, bear in mind if the issue is with a shared sewer, (i.e. shared with at least one other property), and/or off your boundary, the Water Company may be responsible.

 

[Gigagator]

Will look into checking the function of the manholes properly tomorrow when time is a bit more favourable.

For now, I lifted the last inspection cover on the driveway before it heads out into the street - this is the one that this particular toilet drains into and you can see the pipe here. Clean as a whistle as it was when we lifted the covers a couple of weeks ago.



We don't get any other issues with any drainage from the upstairs toilet or basins/shower/kitchen sink and appliances etc, and they all drain out further back up the driveway.

To me this suggests it's either a blockage between the toilet and this manhole, or it is something to do with air like a vacuum.

I found this other old thread that sounds very similar to my issue:
https://www.diynot.com/diy/threads/air-admittance-problem.40368/

I have an IP67 rated endoscopic camera I bought for working on the car that I might jam down there and see if I can see any blockage.