Toilet bowl empty after flush

[Stotty1]

Hi,
Starting from yesterday we noticed a wierd thing with our toilet, the toilet flushes fine (doesn't fill up like when there is a blockage) but gurgles at the end of the flush and empties itself (almost like a vacuum at the end sucking the water out of the bowl). So after every flush there is almost no water left in the bottom of the toilet bowl, meaning I will have to manually fill the bowl with a bucket.
We did notice this happen one night about a month ago but by the morning it was fine again.

Has anyone got any ideas of why this could be happening and how to stop it?

It might be completely unrelated but over the last 6 months we have noticed a dripping sound in our internal soil pipe after we run the hot or cold taps, the sound is only for about 30 seconds at the very end of the draining.
I have not been able to find a leak though.

Thank you for reading and any help you can give.

 

[Burnerman]

As the loo is flushed, air has to enter the system via the soil vent pipe or you get this syphoning effect.......I guess there must be an obstruction in there somewhere. Start by lifting any lids from inspection chambers that may be around.
John

 

[Stotty1]

As the loo is flushed, air has to enter the system via the soil vent pipe or you get this syphoning effect.......I guess there must be an obstruction in there somewhere. Start by lifting any lids from inspection chambers that may be around.
John

Thank you, my first thought was a blockage but as the toilet didn't back up during the flush I dismissed it. But a blockage down the line blocking air flow makes perfect sense.

There is a manhole at the base of the soil pipe, it is seized and I have never been able to lift it, I will see what I can do this weekend to get it up.

Thank you for pointing me in the right direction

 

[Hugh Jaleak]

Where is the affected WC, ground or first floor, and if first floor, it it connected to a vented stack? John is on the same train of thought as I am, but a bit of additional information may help reinforce the diagnosis.

 

[Alec_t]

Does the soil ppe vent through the roof or outside the building, or does it have an air admittance valve inside the building?

 

[Stotty1]

Where is the affected WC, ground or first floor, and if first floor, it it connected to a vented stack? John is on the same train of thought as I am, but a bit of additional information may help reinforce the diagnosis.

Does the soil ppe vent through the roof or outside the building, or does it have an air admittance valve inside the building?

Thank you both for replying. The toilet is on the first floor, the soil pipe is boxed in internally and goes up and out the roof.

Thanks

 

[Dereekoo]

If that vent pipe is clear down to where the toilet outlet tees in then a suction/vacuum cannot occur to the toilet trap, does anything connect into the vent pipe above the toilet connection.

 

[Stotty1]

If that vent pipe is clear down to where the toilet outlet tees in then a suction/vacuum cannot occur to the toilet trap, does anything connect into the vent pipe above the toilet connection.

I can't see as the bathroom is all tiled, but I think the bath and basin waste may go in above the toilet, then it goes straight into the loft.

 

[Stotty1]

So I have just got home and tracked the pipework the best I can following the boxing in.
I'm pretty certain the bath waste goes in just above the toilet waste.
I decided to put some plug hole unblocker in the bath (even though it seems to be running fine) and weirdly the toilet flushed normally for a couple of flushes. But I went back 10 minutes later and it was sucking air through the toilet bowl again. So I am now not sure if the problem is connected to the bath waste or it was just a coincidence.
I'm at a bit of a dead end of what to try next

 

[Johntheo5]

Check the soil pipe vent is clear at the top.

 

[Stotty1]

Check the soil pipe vent is clear at the top.

I did have a quick look from the ground when I got home from work and the grid on top looked clear, I will get some ladders up there tomorrow evening and have a closer look though

 

[Harry Bloomfield]

As above, it is the vent pipe, which is obstructed somehow.

 

[Dereekoo]

I did have a quick look from the ground when I got home from work and the grid on top looked clear, I will get some ladders up there tomorrow evening and have a closer look though

Yes that would be my plan of attack but I doubt it will reveal much unless you can get up on the roof to actually look down/rod it. Something I would be daft enough to sort but some people have more sense

 

[Harry Bloomfield]

I did have a quick look from the ground when I got home from work and the grid on top looked clear, I will get some ladders up there tomorrow evening and have a closer look though

Do you know anyone, with a drone, fitted with a decent camera?

 

[Collectors]

Sounds like a 1/2 blockage & you really need that manhole cover off. It will give you the opportunity to rod both ways up or down the soil pipe.