Water keeps being sucked down the U-bend from my toilet !!

[muffking]

Hi chaps.
I have a plumming related problem (not heating system related though).
My downstairs toilet keeps being emptied of the water in the pan. Every few hours I hear a loud glugging noise to find the water level in the loo going down.
What can cause this???

 

[Nige F]

Probably a blocked drain...down the line

 

[Bahco]

When does this happen?
Is it after flushing the upstairs loo? If so could be due to compression causing loss of trap seal.

 

[muffking]

No mate, it seems to happen every now and then whilst I'm downstrairs (I can hear it when I'm on my PC which is in the next room).

I wondered if a blocked drain could cause this, but as the waste pipe from several houses passed through my garden before going off to the main waterway (or whatever it's called) I would have expected to see (or smell) a build up if that was the case?

 

[ChrisR]

Imagine a "piston" of waste moving down a pipe. It sucks.
Yer normal stink (stack) pipe goes up the side of the house and is open at the top, so air can get in. Unless it's blocked by a bird's nest.
Internal stacks, and stub stacks, are supposed to have a valve on top which lets air in but not poo smells out. These are called Air Admittance Valves, (AAV's) or Durgo's (trade name).
If your loo's waste pipe goes straight into a sewer pipe which isn't vented anywhere, you're stuffed. So you need to work out where all the drains/ sewers go, then decide if there ARE places air should be able to get in, or not.

 

[Bahco]

Strange one this

The only way water can escape is if negative pressure is sucking it out of the pan.
CHris , Kev, DIA, where are you?

 

[ChrisR]

BOO

 

[Bahco]

 

[Slugbabydotcom]

This now and again thing ... Would it be when its windy?

A positive pressure can unseal a trap as when the water swooshes back again after a 'push' there is some water loss from the trap.

NigeF's blocked drain scenario is the most likely from the info you have given

 

[Stoday]

Muffking - ChrisR has the answer. Forget the other responses, they are a load of b******s.

 

[muffking]

Thanks guys. I can totally relate to Chris's answer as the one thing I forgot to mention is that the downstairs loo was built as part of a house extension around 10-15 years ago and the waste pipe goes straight into the sewer so there is little chance of a vent from there.
The only grey area is that I have only noticed this problem since a house 3 doors up the sewage line from me had an extension built recently, but then maybe I just hadn't noticed as I only bought my house about 8 months ago.

 

[Slugbabydotcom]

NOW he tells us!

 

[bathjobby]

the waste pipe goes straight into the sewer

Sounds like you may be getting a syphon effect but you would only expect that when you flush the loo OR something else is going down that stack causing the syphon. Is there something else using this stack (upstairs maybe) whos use would coincide with this problem ?

 

[kevplumb]

waste pipe goes straight into the sewe

should be an inspection chamber somewhere have a look