New shower draining slowly

[oscarthecat91]

I have had a new en suite installed with a 1400 x 800 low profile shower tray (raised on legs due to being unable to cut the joists) with a Mira Atom thermostatic mixer shower installed running off a 35kw combi boiler. This gives a really good flow on the shower

The challenge is the shower waste is only just keeping up with the flow - the tray fills up to a level where you'd think it could overspill but never does. I have noticed the waste seems to flow much faster when there is more water in the tray, it is almost like the water level goes up and water flows out really quickly, the waste then flows more slowly until the tray fills up and almost and empties down a bit in cycles. It is on a 40mm waste pipe, only a meter or so to the outside wall where it goes into the soil stack.

The waste they have installed is this one:

https://www.victorianplumbing.co.uk...seal-shower-trap-chrome-plated-plastic-stw3-r

It has a 50 litres per minute flow rate which is more than adequate however I have just noticed in the small print this has been tested at 120mm head, which is greater than the height of the tray. Could this be the issue?

Is it worth me asking the installer to change the waste to something like this that has a lower flow rate but needs less head?

https://www.victorianplumbing.co.uk/90mm-hi-flow-shower-trap

Would it be a massive job to change the waste with the shower on legs? Was thinking the side panel could come off and it could be done that way, or does the whole tray need removing?

 

[oldbutnotdead]

Problem is most likely the 40mm waste has the wrong fall- sounds as tho it is running slightly uphill or there's an obstruction where it enters the soil stack or in the waste pipe itself. Check that first. (Use a jug, slowly pour water down the waste and listen for water running into the stack/watch the level in the tray and see where it stops rising).
Without pics, hard to tell but generally it's difficult to impossible to get at shower waste without some major damage

 

[ktuludays]

I always fit Mira vortex wastes. They offer really good flow. What you describe sounds indicative of a poor fit or fall on waste pipe

Post pics with panel off side of shower tray

 

[oscarthecat91]

Problem is most likely the 40mm waste has the wrong fall- sounds as tho it is running slightly uphill or there's an obstruction where it enters the soil stack or in the waste pipe itself. Check that first. (Use a jug, slowly pour water down the waste and listen for water running into the stack/watch the level in the tray and see where it stops rising).
Without pics, hard to tell but generally it's difficult to impossible to get at shower waste without some major damage

Here are some photos. The tray has been raised with a riser kit so there must be some fall on the waste. It runs for a meter (if that) through an eaves cupboard and then straight out into the soil stack.

 

[ktuludays]

That pipe doesn't look like it has any fall at all. From your pic it looks perfectly level. Is that the case?

 

[oscarthecat91]

That pipe doesn't look like it has any fall at all. From your pic it looks perfectly level. Is that the case?

It’s has a very slight fall according to this spirit level and would have thought it has more of a fall from the shower tray given it’s on legs?

Is the lack of significant fall likely to be the issue and not the trap?

 

[ktuludays]

It’s has a very slight fall according to this spirit level and would have thought it has more of a fall from the shower tray given it’s on legs?

Is the lack of significant fall likely to be the issue and not the trap?

It would be the 1st thing I'd check. Can you post a pic of trap under tray?

 

[oscarthecat91]

The side panel is siliconed on so would rather leave that for now and remove if I need to get the plumber back.


Interestingly I have just poured multiple large 2 litre jugs of warm water straight down the drain as suggested above and tried the shower after and the issue resolved itself with the shower draining really well.

is it likely I’ve broken an air lock or maybe their was tilers mess down there?

 

[oldbutnotdead]

Tilers mess is quite likely, especially in that double elbow arrangement at the stack. Which looks like gutter pipe to me....if you have separate surface and foul water drainage that might be another problem...
EDIT Nope, I'm wrong, that is 110mm.
You'll need to keep on top of hair etc in the shower trap, any sort of build-up in that double elbow will be impossible to clear without scary chemicals

 

[oscarthecat91]

Tilers mess is quite likely, especially in that double elbow arrangement at the stack. Which looks like gutter pipe to me....if you have separate surface and foul water drainage that might be another problem...
EDIT Nope, I'm wrong, that is 110mm.
You'll need to keep on top of hair etc in the shower trap, any sort of build-up in that double elbow will be impossible to clear without scary chemicals

the existing bathroom drains into a hopper which links with the exterior guttering except the toilet which goes into the soil pipe. Is having the new shower waste into the soil pipe a problem?

 

[oldbutnotdead]

Some areas have separate drainage systems for surface water and foul- running a shower or bath waste into a surface water system is frowned upon quite hard by water board. If you have combined drainage (so everything goes into one pipe) then you're fine. Shower into soil pipe should be ok.

 

[dilalio]

You have a Durgo (AAV) fitted to the top of the soil stack.

Change it to a proper vented stack that goes around the eaves and above the roof.

Your issue is caused by air trying to escape out of the shower waste, whilst water is going down it. You have a cushion of air that the waste water is trying to push past.

Like trying to quickly pour water out of a gallon container... You get a glug, glug action.

 

[Madrab]

How long is that run and why is the pipework sitting where it is in that room? That just isn't right at all. The biggest concern is that the 'plumber' actually agreed to fit the waste like that. It should at least be run along the wall alongside the soil pipe seems to be in there too?

You can't change the waste/trap to 90mm as it wouldn't fit your tray. In all honesty that's probably one install where I would consider using a 40mm removable tray waste and a shallow bath trap to maximise flow, then up it to a 50mm waste pipe.

As mentioned your stack isn't fully vented either so the minute the waste pipe fills it'll struggle to flow properly due to back pressure, that and it'll be trying to overcome the trap seal too so it has a lot to push against without much pressure from the water until the water fills the tray. See it all too often, small tray waste, too long a waste pipe run, waste pipe not large enough to help with the flow and not enough fall and then it's compounded with a AAV on the top of the soil pipe. Was it a 'bathroom installer' or a plumber that performed the work?

What are they saying about it, IMO it's their issue to sort. Did they not test it (run the shower for at least 5 mins to test the outflow properly) before handing over?

 

[oscarthecat91]

How long is that run and why is the pipework sitting where it is in that room? That just isn't right at all. The biggest concern is that the 'plumber' actually agreed to fit the waste like that. It should at least be run along the wall alongside the soil pipe seems to be in there too?

You can't change the waste/trap to 90mm as it wouldn't fit your tray. In all honesty that's probably one install where I would consider using a 40mm removable tray waste and a shallow bath trap to maximise flow, then up it to a 50mm waste pipe.

As mentioned your stack isn't fully vented either so the minute the waste pipe fills it'll struggle to flow properly due to back pressure, that and it'll be trying to overcome the trap seal too so it has a lot to push against without much pressure from the water until the water fills the tray. See it all too often, small tray waste, too long a waste pipe run, waste pipe not large enough to help with the flow and not enough fall and then it's compounded with a AAV on the top of the soil pipe. Was it a 'bathroom installer' or a plumber that performed the work?

What are they saying about it, IMO it's their issue to sort. Did they not test it (run the shower for at least 5 mins to test the outflow properly) before handing over?

The room the en suite has been built in is an attic bedroom and the pipes in the photos have been run through a small area of the eaves which was previously sealed off and is now accessible via an access door they have had put in. The run is 1.2 meters max.

It has been fitted by a plumber with 20 years experience apparently. They are saying it’s acceptable as it doesn’t overflow the tray.

I’m not happy with it so will need to get them back. The waste isn’t accessible without cutting the ceiling below so is the best solution fully venting the stack?

 

[Madrab]

They are saying it’s acceptable as it doesn’t overflow the tray.

Nah, wouldn't buy that excuse at all. It shouldn't top out in the tray unless it's really shallow. What are they saying, if the waste starts to restrict even slightly from gunge/hair etc, then does it just run out the door?? The waste and run should be setup to drain properly without pooling to the top of the tray edge. If it can't then the tray should be changed to take a 90mm waste, raised higher, deeper tray used and then maximise the waste run size and fall. Proper design is what was needed.

To easily test whether the stack needs positive venting or not by removing the AAV(durgo) off the top and see if that then allows the tray to drain properly. If it does then the soil pipe needs an open vent and will need taken up and over the gutter.