Shower Waste

[bw65587]

We've had a new extension built for a new bedroom with en suite. The fast flow shower waste in the new en suite shows some strange behaviour. Firstly, when you flush the loo the chrome shower waste rocks up and down. Secondly, sometimes the shower water flows out of the shower tray fine and other days you have to lift out the chrome part to get the water to flow out. If you then put it back it carry's on working fine. I just don't understand it.

I've uploaded a couple of photos to show the new SVP. The lower of the two waste pipes is from the basin and the higher one is from the shower.

The SVP has an external air admittance valve fitted.

Any ideas?

Many thanks!

 

[Hugh Jaleak]

There an issue with the drains, and the water cannot get away properly. The AAV lets air in but wont allow positive pressure out. If the drain is blocked, or has a belly in it, (a low spot where the pipe is sitting full of water), then this effectively seals the pipework. When you discharge, the water needs to displace the same volume of air, so this air is looking for the easiest way out.

Shower waste flow is possibly related to the same issue, lifting the chrome part allows a slightly better flow, which is then inducing syphonic action in the waste pipe, which begins to suck the water out, giving the impression is flowing better.

I'd check the drains have actually been connected, it's not unknown for Builders to 'forget'.....

 

[just pumps]

The higher one (Shower), is it the angle of the camera or is that runing slightly uphill?

 

[Hugh Jaleak]

Good spot JP, unless my eyes are that bad, it certainly isn't running downhill!

 

[bw65587]

The higher one (Shower), is it the angle of the camera or is that runing slightly uphill?

Someone did look at this some weeks ago as it does look from the ground like there is very little fall on the waste pipe. They said there was a slight fall. Would this fall being very slight possibly be causing it on its own? Should I get it changed to be greater? Thanks!

 

[Hugh Jaleak]

Spirit level will tell you exactly, needs a slight fall on it at a minimum. Still wouldn't cause the issues you describe when the WC is flushed though.

 

[just pumps]

Spirit level will tell you exactly, needs a slight fall on it at a minimum. Still wouldn't cause the issues you describe when the WC is flushed though.

Agree, shame you can`t lean through the window above and remove the AAV to experiment. Nearest manhole or inspection close?

 

[bw65587]

Spirit level will tell you exactly, needs a slight fall on it at a minimum. Still wouldn't cause the issues you describe when the WC is flushed though.

Thanks. I didn't think it would resolve it as it's air that's coming back up through the shower waste trap like you've said. I'll investigate the drain itself as suggested.

 

[bw65587]

Agree, shame you can`t lean through the window above and remove the AAV to experiment. Nearest manhole or inspection close?

I could do that. Not sure what my experiment would be though! Ha-ha! Nearest manhole is close.

 

[Hugh Jaleak]

Check manhole, if this is empty, get someone to flush WC, you should hear it coming before you see it. Expect a rush of water, a steady trickle indicates a problem.

Removing the AAV allows positive pressure to vent when WC is flushed, rather than bubble back through the shower.

 

[bw65587]

I'd check the drains have actually been connected, it's not unknown for Builders to 'forget'.....

You were absolutely spot on! Investigations this morning have confirmed that there is no connection between new foul drain and existing! Job getting done on Thursday but tomorrow they're emptying the new drain. Nice!!! Hugh Jathanks to you!