Discussing over dinner the WCs we have known and loved (as one does) the conversation turned to a new-build house we visited in Derbyshire.
The downstairs WC and hand basin seem to be coupled. The WC flush appears to operate normally but when one empties the contents of the washbasin, the water in the u-bend of the WC is sucked down a little.
It doesn't appear to be causing any harm but is this normal these days? Or just normal for Derbyshire?
Nick
More likely just a less that perfect drainage system which syphons some water out of the dunny when the basin is emptied.
bad plumbing design causing syphonage simple no proper back venting
Not unusual - a one way air valve fixes this, but do you care?
As long as the U-bend doesn't let pongs in, it's fine.
Is this a separate basin, or one of those "ultra compact" solutions for cloakrooms where the basin is built into the top of the WC cistern?
If it is a separate basin then it suggests that the installer has a non vented soil pipe, but has not included an air admittance valve.
is a dunny the same as a Scottish cludgy ?
Wouldn't it also be solved by a deeper trap? Suction would pull it down and maybe even pull some air through, but there'd be enough left in the other leg to even out and still retain a seal afterwards.
Maybe a bird had built its nest on top of the soil pipe vent.
Confession time. When I was little (maybe 5 years old) I knew a lot of the houses on my route to school by the pattern that the waste pipes made on the outside wall. (OK, I was WEIRD!) And I was intrigued by the houses which had a very long 2" bath/washbasin pipe that sloped down to the 4" vented soil pipe but which also had another pipe that sloped
*upwards* from the bath pipe to join onto the soil pipe higher up. I presume that was an anti-siphon pipe.
The soil stack probably has one of those automatic vents tucked away somewhere rather than being open and vented outside- often via the roof. The vent is one way - it allows air into the stack but stops smells etc from leaking out.
In an open system, as the sink empties air can enter freely.
With a vent, there can be a delay as the vent doesn’t open immediately.
Would the amount of water going down a small sink plug hole be enough to open the air admittance valve? When flushing the bog you have 4/6 litres of water in around 5 seconds
ISTR the building regs impose a maximum length of waste pipe to a stack before a AAV is required (to prevent it sucking air out of the bath/basin trap)
Yep.
cool
wouldn't work with a good old three gallon flush
puff pipe
which everybody ignores
it would get sucked in
I have come accross edjits the stick durgo valves OUTSIDE .....
and the bath should have a separate connection into the stack below the wc and the whb above but who does that now a days
Have something to add? Share your thoughts — no account required.
Ask the community — no account required