Water backing up into bathtub

[E.T.]

Hello,

I’d be very grateful for some advice on a plumbing issue we’re having.

We’ve moved into a second floor flat that we’re renovating. Behind the bathroom wall is a recess within the building. The waste pipe heads through the bathroom wall and joins the building communal waste (I believe, although I haven’t actually seen behind the wall). We’ve been showering for weeks and the bath has drained with no problems.

The washing machine arrived and yesterday we connected this via a spigot in the waste trap under the kitchen sink. This is connected to a 4m long 50mm waste pipe that runs through the kitchen wall into the bathroom (under the tub) and out of the flat through the shared wall into that recess to join the building communal waste.

Our 50mm waste pipe is a single waste pipe that the bathtub is also connected to (via a u bend trap and 40mm pipe).

The bathroom sink and toilet waste pipes head through the bathroom wall independently into the recess.

When we ran the washing machine dirty water backed up into the bathtub. Loud gurgling noises could be heard from the kitchen sink waste during and after the washing machine cycle.

We closed the bathplug pop up and opened the 40mm waste pipe, had a look, inserted a rod to clear any blockages. There didn’t seem to be any (which made sense to us as we’d had no bathtub draining problems thus far).

When the bathtub pop up was closed the gurgling sound in the kitchen waste increased, making us wonder whether it might be something to do with air lock?

We opened the bathtub pop up and this drained eventually but very slowly. This morning when I showered the bathtub wasn’t draining properly.

We could replace the long waste pipe with a new one. We’re just a bit of a loss as to why the bathtub won’t drain now when this was working perfectly fine before.

Any advice would be much appreciated!

Thanks

 

[terryplumb]

Blockage in pipework somewhere.
Do you have building maintenance for communal issues ?

 

[E.T.]

Thanks Terryplumb.

There is a management company for the building and yes we could ask them if we think it’s a blockage in the communal pipe.

It just seems odd that this has only happened after we’ve connected the washing machine - i.e. the bathtub has been draining into the same waste pipe without any problems until now.

 

[terryplumb]

If you have a two inch diameter waste pipe that was PARTIALLY blocked ,and washing machine connected ,the velocity of the pumped waste water from it may have dislodged some crud in the pipework to another position ,further increasing the restriction.
Or it may be pure coincidence.

 

[E.T.]

Yes, that might be it. Our waste pipe within the flat isn’t a new one so I suppose the washing machine may have disturbed the old gunk and pushed this down the pipe beyond the point where the bath waste joins.

So I’m inclined to poor some drain unblocker down the bath waste, replace our long internal waste pipe and see where that gets us to.

Thanks

 

[blup]

The steep fall of the long waste pipe and the pump of the washing machine create a (partial) vacuum that forces the waste into the bath.

Blup

 

[Hugh Jaleak]

Washing machines pump out the water at a fair rate of knots, whereas a bath will drain by gravity, so will empty in its own time according to the capacity of the pipework, whereas washing machine will discharge at a constant rate, and if the pipework cant handle the flow, it backs up.

Seen similar with a bath and shower connected to the same run. Girl got out the bath and pulled the plug, water couldn't get away quick enough, erupted into the shower, overtopped the shower tray and flooded the bathroom. She'd gone into the bedroom to dry her hair, by the time she realised what was happening, water was dripping through the kitchen ceiling below.

 

[E.T.]

Thanks this is helpful. If a vacuum were the issue, would an air admittance valve help?

 

[terryplumb]

Thanks this is helpful. If a vacuum were the issue, would an air admittance valve help?

If the bath doesn't drain now ,and the wash Mac isn't operating ,how can it be a vacuum issue ?

 

[terryplumb]

The steep fall of the long waste pipe and the pump of the washing machine create a (partial) vacuum that forces the waste into the bath.

Blup

In a two inch waste pipe ,with the drain from the washing machine connected to an open sink waste ,I don't think so.

 

[blup]

Thanks this is helpful. If a vacuum were the issue, would an air admittance valve help?

It is worth trying that if only to exclude the possibility of siphonage or backflow in your system. If that doesn't work ask the freeholder to check that the main soil pipe is properly vented and unblocked.

Blup

 

[blup]

This video might assist:

Blup