Shower drains slowly

[dcleal]

Hi,

I have a newly installed shower. It drains perfectly when you run the shower with plain water for as long as you want. Then if you actually shower with shampoo, the soapy water seems to create some kind of film or something and the water doesn't drain, and eventually the shower tray overflows.

Is this a common thing? Is there anything to do?

Thanks in advance

- Dave

PS. The waste is one of these: https://www.ukbathroomstore.co.uk/simpsons-sthfw6190-high-flow-waste

 

[PrenticeBoyofDerry]

Only thing you can do is either, check the fall of the flow is suitable, keep the pipework clean or don't use soap products.

 

[bernardgreen]

Foam travels very slowly through pipe work. Much slower than the same volume of un-foamed water.

Two main reasons

1) The air trapped in the bubbles increases the volume of fluids that have to get through the pipe.

2) The surface tension of the water is reduced ( by the soap ) so more of the water adheres to the pipe instead of flowing freely.

In a shower drain, other than gravity, there is no pressure to force the foam through the pipe. Water enters the shower under pressure but has to leave with no pressure exerted on it. Hence the diameter of the drain pipe should be several times the diameter of the shower feed pipe.

 

[Nige F]

Do you know where the waste runs to? is it accesible ?

 

[Groovejet]

One thing you can do is remove the chrome cover on your shower trap to unearth the bowl that creates the trap that stops fowl smells coming back.
Check the distance to which the chrome cover with the tube goes into this plastic bowl.
You'll find its there's only a small gap between both pieces to which water can escape.
You need to either:
1- cut cover tube shorter to create a bigger gap to which more flow can escape
2- in the bowl create more holes ( relief) to which the water will pass through the trap faster.

Or both1-2

I've had to do this many times, maybe it's cheap traps?? I don't know.
All I do know is that on a install I've fitted shower tray and pipe with correct fall and correct size pipe and this scenario happend and all you can do is what I've said as most times it's impossible to replace the trap without causing damage and heaps more work.

 

[dcleal]

Thanks for the replies!

Apparently (according to the various women in the house) not using soap products isn't an option

The waste isn't accessible for a while (runs under a tiled floor for seven feet).

@Groovejet I was thinking along similar lines, so this sounds right. But, those same women won't be happy if I make modifications that make things worse, so, please can I get ask for a bit more detail on how you do this?

This is roughly what I have (not to scale!)... the top of the cross piece is just a plastic cross, there seems to be plenty of space for water to get into the cup. I think that the issue is that the gap between the cup and fixed part around it is really small, though I could be wrong. Where would you make holes? Thanks in advance....

 

[terryplumb]

take the " cup " out completely ,as well as the cross piece and chrome lid.check inside pipe outlet is clear. leave it all off ,use shower with more soap than you can muster ,and see what the result is. if it still does not drain the pipework is obstructed .or too small , too many bends or incorrect fall.

 

[Hot&Cold]

Is the shower tray is one of those low profile 40mm products with the waste fitting hidden away in the corner and no dedicated water flow ways in the tray floor to direct water to the waste fitting ?

 

[dcleal]

OK, so I mis-drew this yesterday - just updated it. The chrome-ish piece seems to make very little difference to flow, it's basically harmless.

If I remove the cross piece and leave the cup in it drains perfectly. If I remove the cup but keep the cross piece it's not quite so good but still perfectly fine. It seems to be just the combination of the two that's an issue.

The shower tray is fairly low profile, but seems to drain OK when the trap drains OK.

I'm toying with the idea of shortening the descending part of the cross piece. as long as it extends below the top of the cup, it seems to me that I have a water seal to keep the smells at bay, and if feels like this should increase flow. Anyone see a problem with this plan?

 

[terryplumb]

can you post pics of the components ,and the tray (showing inside trap )

 

[Nige F]

And for some reason your previous picture isn't showing - can't open it ??

 

[terryplumb]

nigef ,if you mean the sketch ,op has re drawn it ( amended original ) .the only pic I have seen is a link showing the suppliers pic and shows nowt.

 

[dcleal]

Hmm.. Just found the manufacturers' picture online: https://www.crosswater.co.uk/files/STHFW6190_specification.pdf, this is probably a better pic than mine anyway!

The lower picture shows the pieces I can easily remove, I'm thinking of shortening the inner piece with the cross on top.

- Dave

 

[terryplumb]

Dave ,the water seal is made between the tube ( of the cross piece ) and the pot ( cup as you describe it ). the length of the tube dictates the " depth " of seal. this type of trap empties by displacement. when the tube is inside the pot ,there is a gap between the end of the tube and the bottom of the pot ,and all the water has to pass thru it. what keeps the pot tightly in position in the waste housing ??? if it can " float " up ,it will reduce the gap and impede flow. your suggestion of making the tube shorter is basically along the same lines ,but will reduce the trap depth.I do not see why you should need to do this ,unless the manufacturer has got their design / clearance tolerances very badly wrong. however I don't think you can come to any grief cutting half an inch off the bottom of the tube to help resolve your issue. make sure you smooth it all off after cutting if you go down that route.

 

[dcleal]

Thanks for the continuing interest! The pot is positioned tightly because it eight fins sticking on the outside that click into slots in the waste housing. The gap between pot and housing looks pretty small (2mm?). The reason I'm focused on the relationship between the tube and the pot is that if I put either in without the other, it drains perfectly, it's only when I have both that I have a problem. I've now find that the waste costs a princely 13.20, so I plan to buy a reserve before I start hacking at this one