Toilet water level low after heavy rain??

[Aquaman]

During last weeks heavy rain, my toilet bowl started bubbling and the level rose. After the rain stopped everything went back to normal but now 3 to 4 days later the water level in the pan is a lot lower that it usualyl.

Will this correct itself or is there a problem?? And if so is it United utilities (supplier) problem to fix as it was there drain that started the issue.

Thanks in advance for any answers!

 

[Onetap]

It's a U-bend, the water levels on both sides will be level IF the air pressures on both sides are the same.

There's a negative pressure on the drain side which suggests there is no ventilation into the drain (via S&V pipes) or there is a blockage. I'd lift any manhole covers and rod the drains if there's any sign of a blockage. If the drains are shared with other properties, it's the drain companies problem.

 

[Aquaman]

It's a U-bend, the water levels on both sides will be level IF the air pressures on both sides are the same.

There's a negative pressure on the drain side which suggests there is no ventilation into the drain (via S&V pipes) or there is a blockage. I'd lift any manhole covers and rod the drains if there's any sign of a blockage. If the drains are shared with other properties, it's the drain companies problem.

Cheers for the reply onetap.

I have looked into the manhole cover which is outside almost directly in line with the toilet soil pipe (Its a bungalow so the toilet is at ground level) There is no blockage, it clear from the toilet to the manhole and continues away to the main sewage with no problem. As I can't see anyform of vent piping, how do you get the pressure equal the drain side???

 

[Aquaman]

Sorry to bump....but are there any Monday morning drainage experts about to help with the above?

 

[HERTS P&D]

Open the manhole and get someone to flush the toilet while your looking in the manhole, if there is no blockage then the toilet water level should go back to normal and the water will flow into your manhole and into the main sewer.

Bungalow's do get blocked more often than normal houses due to the bungalow having a larger foot print and no height of water when the toilet is flushed.


Andy your local drainage engineer.

 

[TheVictorian]

Could it be if there is loads of rainwater pumped into the soil stack then it's creating suction from the toilet? Could be a birds nest in the top of the stack?

 

[Aquaman]

Open the manhole and get someone to flush the toilet while your looking in the manhole, if there is no blockage then the toilet water level should go back to normal and the water will flow into your manhole and into the main sewer.

Bungalow's do get blocked more often than normal houses due to the bungalow having a larger foot print and no height of water when the toilet is flushed.


Andy your local drainage engineer.

Cheers for the reply Andy. When I lift the manhole cover I can see the water flow out and into main drain there is definitely no blockage. But the water level in the toilet pan is a lot lower that usual and no matter how many times I flush it, it still stays at the same level....... which is about half its usual level from before the incident.

Some one mentioned negative pressure on the drain side affecting u-bend....(here's the I don't know what I'm talking about question) do I have to re-pressurise or something???

 

[75pete]

With the manhole cover removed and the loo flushed, what is the level like, still low or back to normal?
Pete

 

[Aquaman]

With the manhole cover removed and the loo flushed, what is the level like, still low or back to normal?
Pete

its still low

 

[HERTS P&D]

You might have a blockage from the toilet to the manhole, did you have a toilet rim freshener on the bowl?

You could try a set of rods and rod the toilet with the rubber plunger.

Andy

 

[Aquaman]

You might have a blockage from the toilet to the manhole, did you have a toilet rim freshener on the bowl?

You could try a set of rods and rod the toilet with the rubber plunger.

Andy

Hi Andy......toilet to man hole has definitely got no blockage.

What's this negative pressure on drain side??

 

[HERTS P&D]

If the manhole is open and the toilet is flushed then the pressure will be equal, unless there is a blockage. The next thing to do is have a camera put up the drain line from the manhole to the toilet.

Andy

 

[75pete]

The new low water level, just how low is it, is the trap exposed? It just could be that the old level was to high, as you say, the new level after storm in your area, may have given the sewer a flush thus a quicker flush and lower new level.

 

[Onetap]

What's this negative pressure on drain side??

As stated above, it's a U-bend trap with water lying in the base of the U.
The water will be at the same level on both sides of the trap when the air pressures are the same on both sides.

If the pressure is higher on the drain side, then the water level will be pushed down on the drain side and will rise on the house side until the water seal is broken and bubbles of sewer gas will enter the house. This is what was happening previously and it suggests there may be a blockage. The gas should be vented from the top of a soil and vent (S&V)pipe. It could happen if the original S&V pipes had been removed and air admittance valves installed.

If the pressure is lower (negative, less than atmospheric pressure) on the drain side, the water level will be sucked up on the drain side and will be lower on the house side. This is what is happening now and guess what it may indicate? It suggests there may be a blockage since the drains should be vented through a S&V pipe so that they are always at atmospheric pressure.

I'd have expected the toilet U-band level to revert to normal after flushing with the manhole open, since that would allow air into the drains.

It might also happen if you've installed a FOGB ventilation plant and your house is at positive pressure. I think you might have noticed that though.

I'd suggest you find your S&V pipe and check for blockages ( or the S&V pipe having been removed or amended, e.g., during a loft conversion) between the toilet connection and the top of the S&V pipe.

PS Another thought; the rainwater drains are usually(but not always) separate from the foul drains, since the rain water will usually discharge into a nearby stream. If the toilet is an alteration, it might be wrongly connected to the rain water drains. That could explain why the rain caused a change in level and why there's no ventilation into the drains.