I've noticed during the recent bout of rain that our upstairs plumbing exhibits some strange behaviour when the rain is heavy, with the toilet and bath gurgling and bubbling. Our waste water and surface water drainage are on a shared system, so my guess is that the influx of rainwater into the drains possibly causes some sort of backlog. Anyway, that's just my speculation. Really hope somebody can have a go at diagnosing this as there's not much left in the family piggy bank! I am saving up for a completely new roof, so anything like this helps.
Our plumbing set-up
House is detached but shares a private sewer with next door, which then connects to the main public sewer in the outside road. At the back of the house is a soil stack which terminates below the abutment/roof line of a rear single-story extension. There is a flat area on the roof near to the stack and below the bathroom window, and I can see a small vent here suggesting there must be some sort of air admittance valve. The upstairs bath, shower and toilet appear to drain into the stack fairly close to the top of it. The stack then runs down into the kitchen (behind the plasterboard), where a downstairs WC/utility drain into the bottom of the stack. From there, the foul waters run under the extension to the private drain, with the kitchen drainage and two rainwater downpipes joining the sewer via outside traps. No visible manhole cover.
The Problem
During heavy rain, the bath will gurgle/bubble when the toilet is flushed. I can see water coming up from the trap into the bath. When the shower is used, the toilet pan will bubble away - I can see large air bubbles coming up from out the U-bend and up to the surface. If flushed during a shower, the bath gurgles quite violently, throwing water up into the bath. This suggests a lot of air is being pushed back up? No other plumbing in the house shows signs of problems, there are no odd smells, no visible leaks. After the rain has stopped for a while, everything returns to normal. When I say 'normal' I have noticed that when the toilet is flushed, water drains away quite quickly and continues to drain until the pan is almost empty, when there is a loud burp/gurgle and it then fills mainly back up.
I've possibly waffled a bit here and missed out bits. If anybody doesn't mind sharing their thoughts I'll answer whatever I can. We don't flush anything you shouldn't (we are strict on this). I have only replaced one part which was the P-trap on the shower (old one was broken and leaking), however this was only recently and has made no difference.
Our plumbing set-up
House is detached but shares a private sewer with next door, which then connects to the main public sewer in the outside road. At the back of the house is a soil stack which terminates below the abutment/roof line of a rear single-story extension. There is a flat area on the roof near to the stack and below the bathroom window, and I can see a small vent here suggesting there must be some sort of air admittance valve. The upstairs bath, shower and toilet appear to drain into the stack fairly close to the top of it. The stack then runs down into the kitchen (behind the plasterboard), where a downstairs WC/utility drain into the bottom of the stack. From there, the foul waters run under the extension to the private drain, with the kitchen drainage and two rainwater downpipes joining the sewer via outside traps. No visible manhole cover.
The Problem
During heavy rain, the bath will gurgle/bubble when the toilet is flushed. I can see water coming up from the trap into the bath. When the shower is used, the toilet pan will bubble away - I can see large air bubbles coming up from out the U-bend and up to the surface. If flushed during a shower, the bath gurgles quite violently, throwing water up into the bath. This suggests a lot of air is being pushed back up? No other plumbing in the house shows signs of problems, there are no odd smells, no visible leaks. After the rain has stopped for a while, everything returns to normal. When I say 'normal' I have noticed that when the toilet is flushed, water drains away quite quickly and continues to drain until the pan is almost empty, when there is a loud burp/gurgle and it then fills mainly back up.
I've possibly waffled a bit here and missed out bits. If anybody doesn't mind sharing their thoughts I'll answer whatever I can. We don't flush anything you shouldn't (we are strict on this). I have only replaced one part which was the P-trap on the shower (old one was broken and leaking), however this was only recently and has made no difference.
