Bath waste flows back into shower

NickB_99 · 19 Sep 2009

Hello all,

Quite concerned about this - please help!

I'm currently in the process of having a bathroom fitted. Today was the first time I've been able to fill the bath with water to use, with all waste connected etc.
I found that when the bath was emptied the water flows out ok, but seems to backup into the shower part of the waste system. Initially it makes a bubbling noise at the shower and then a significant amount of water comes up out of the shower plughole and into the tray

Is this normal??

I don't think it will be trivial to fix as now the WBP ply is screwed down over the floor (prior to tiling) and bath secured/sealed to wall.

I can imagine he will not be overjoyed.
The fitter will be back on Monday and I was after some background info first.

TIA

dextrous · 19 Sep 2009

Needs to fit a different trap for the shower - something like a hepvo which is self closing and prevents backpressure.
Alternatively he needs to fit an independent waste run from the bath that doesn't link onto the shower run.

NickB_99 · 19 Sep 2009

dextrous said:
Needs to fit a different trap for the shower - something like a hepvo which is self closing and prevents backpressure.
Alternatively he needs to fit an independent waste run from the bath that doesn't link onto the shower run.

Many thanks for a prompt response Dextrous.
(I don't normally stray from the plastering forum much!)

I'll discuss it with him Mon morning.

I would imagine the change of trap will involve taking up less WBP off the floor....up to him I guess which is an easier solution for him.

Is this a common problem when plumbing in waste for showers & baths, or have I been unlucky?

dextrous · 19 Sep 2009

Bit unlucky, but not entirely unusual. Now is the time to sort it out though, since it's entirely possible that the current layout will lead to the bathwater causing a loss in the water seal in the shower trap (and possibly vice-versa) which will allow pungent smells into the bathroom if the waste pipe is bossed into a soil stack, or a cold draught if it's going into a hopper outside.

JayJay1978 · 19 Sep 2009

It shouldn't happen, done properly no water should flow back into the shower tray from the bath, they should have seperate wastes ideally or if piped together done to the corect fall and is the run is too long then go to 50mm wastepipe.

Tell him this is unacceptable and that he'll need to rectify before tiling.

Do it right or not at all.

doitall · 19 Sep 2009

I agree with JayJay, obviously an installer error.

An HepVo will solve one problem, but avoid it at all cost, as the back will still be there and block the shower waste for a past-time.

bengasman · 20 Sep 2009

I have a strong suspicion that your plumber has not paid attention to the required fall for the waste pipe.
If the fall is less than required, there is a significant chance that the pipe will block up on a regular basis.

If there is a rodding eye where the pipe comes out of the wall, and there should be, you can remove the cover and stick a length of 22 mm copper pipe in. When the copper pipe is in the waste pipe for about 2.5 metres, leaving about half a metre sticking out, you should get a fair idea of the fall.
If memory serves, the minimum is 2%, though I personally always stick to 4% if half possible.

I have yet to receive a complaint of backflow or blocking on any waste I have installed.

dextrous · 20 Sep 2009

doitall said:
I agree with JayJay, obviously an installer error.

An HepVo will solve one problem, but avoid it at all cost, as the back will still be there and block the shower waste for a past-time.

So it would. Oops, silly me

Always fix the cause, not the symptom

I was more concerned about the loss of seal really and took my eye off the ball

JayJay1978 · 20 Sep 2009

You can't beat a good properly installed waste system where a bath or basin drains in no time with a nice gurgle. It's amazing out many people think water will run uphill.

SUPERPLUMBER · 20 Sep 2009

just out of interest, was the shower you used to have either quite a deep one or was it standing on a plint? And the replacement a slim one sitting on the floor?

NickB_99 · 20 Sep 2009

SUPERPLUMBER said:
just out of interest, was the shower you used to have either quite a deep one or was it standing on a plint? And the replacement a slim one sitting on the floor?

Just happened to be online checking this post - timing!

I'll try to describe....
Bathroom is rectangular shaped.

Originally it was a bath with shower at one one end.
Changed for standalone shower and a separate bath on the other wall.

The shower equipment is where it used to be, but all waste plumbing is new.
The shower is diagonally opposite the soil pipe - waste flows along the floor cavity along the short wall, right hand elbow under the bath and a run up to the soil pipe with a T connector where the bath waste fits in to the run. I am sure there are U bends in there also.

Yes, the shower is a slim one sitting on the floor. From looking at the situation again, the bath plughole is prob 6" higher than the plughole of the shower.
I also noticed this morning that the fuller the bath is when the plug is opened, the worse it is. More head?

I hope the description helped.
If not let me know, and I'll try to do a sketch or something.

It's also worth saying that they had a pig of a job with the internal soil pipe and they did well to get such a neat finish.
It has also had a waste and soil feed from the opposite side where an ensuite will go in in the next room.
Possibly the height of the bath/shower waste boss came up just slightly higher than intended in the adjustments.

bengasman · 20 Sep 2009

Do you have any idea what the fall actually is? Unless it is a very small bathroom, it should be at least 100 - 150 mm.

NickB_99 · 20 Sep 2009

bengasman said:
Do you have any idea what the fall actually is? Unless it is a very small bathroom, it should be at least 100 - 150 mm.

Bathroom is approx 2m70 by 2m10, so not big.

All boards are down so can't see from above, but I can access the internal soil pipe cavity from the room underneath.
From what I can see, the waste comes into its boss about 70mm below floor board level.
Estimate 1m90 length of run from bath plughole.
So at best, by my calc, no more than 2.1degs can be achieved.
I'm guessing this is too low?

bengasman · 20 Sep 2009

2 degrees is more than 2%, so that would be fine. The $64,000 question is: could it be achieved, or has it?
You can easily check doing what I described above.

sooey · 21 Sep 2009

He said it's a shallow tray, sitting on the floor. So if the boss is only 70mm below floor level there's definitly not going to be much of a fall, if any.

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Bath waste flows back into shower

dextrous

dextrous

dextrous

Similar threads