Drain Gully Bubbles When Toilets Are Flushed

[fosbie]

I have a drain gully at the back of the house which is just used for sinks to drain into, but recently it has started to bubble up a couple of times whenever a toilet is flushed in the house.

I'm not sure if this is relevant but I've tried poking a stick into the drain and it seems to have a lot of gravel at the bottom and I can't seem to feel any continuation of the pipe that would let the water out, is it possible that this is a blockage that might be causing it?

 

[Hugh Jaleak]

Educated guess says you have a blockage, but further down the line in the sewer. As the toilets are flushed, the water from the toilet is displacing air in the drain, causing positive pressure in the pipes that cant escape other than bubbling back up through the gulley. (Gulley and toilets will be connected underground.)

You need to lift manhole covers and trace the problem, (it may well be neighbours are affected too). Grit in the gulley needs removing but wont cause the bubbling issue, that is usually a sign of bigger problems elsewhere.

Gulleys form a 'U' shape, to trap water and provide a seal against foul odours from the sewer escaping, the outlet will rise upwards before turning horizontally to the outlet.

 

[fosbie]

Thanks for the reply, you were spot on. I lifted the manhole cover at the end of our drive and found it was almost full to the top! After I got it to drain away with a bit of rodding I found that a few bits of brick and rubble had fallen off the inside of the chamber and blocked off the pipe. All sorted now.

Thanks again for the advice!

 

[Hugh Jaleak]

Glad to be of help.