very slow running shower drain

[JohnOfChelmsford]

@old duffer - you're a legend for taking time to post that Mira fix - had the exact same issue for a loft shower, and drilling a hole the opposite side as suggested sorted it, just as parents were over to stay, who discovered it was nearly flooding as so slow to drain!

Had actually been using shower for a while fine (a few showers a month) but recently found a slow leak coming down through ceiling in bedroom underneath. Cut a hole in ceiling to inspect, and turns out the "waste seal" under tray was pinched\torn and after a few mins of hot shower it was letting water through. Mira sent out a whole new assembly - and when replacing, i noticed plumber never fitted the "bracket seal" - so when i reassembled with that added, and a not torn "waste seal" - i could sense it was all more 'air tight' and was operating as designed (i.e. "waste tubes" and waste body forming a water trap'). But while we fixed one issue, we started seeing the 'airlocking' @Madrab described , which the hole sorted....but believe i'm reading that a better fall would have sorted too?


Main question i have now though - is the fact i drilled an 8mm hole (on opposite side of drain escape) meaning that i'm going to get sewer gas up? Is that what a self-venting piece should prevent. Like OP, my fall probably isn't great, and goes out to the soil stack with AAV. I don't believe i have a self venting section of pipe work under shower tray- there's just an elbow coming off vertical waste outlet and a white flexi bit for a half-meter that i can feel connects into a solid pipe and goes outside to meet soil stack. should i replace flexi run with a self seal or something suitable? Any advice appreciated.

Update: Confirmed it's a mcalpine stiff flexi (with the smooth inside), so not too bad, thinking i use the flexiness to try connect to the opposite waste side (horizontal one) so that creates more of a fall, as being connected to the vertical means it's a bit lower). i'll take a pic later...

 

[Nige F]

1 Thing I is those 90 degree elbows 92 degree bends are proper. A sani snake will go round them - not those 90 square mostrosities.

 

[Madrab]

+1 - Couldn't agree more -

Always best to use swept bends on inaccessible waste pipe - 90deg elbows are just a mare waiting to happen, especially in slow running shower waste runs.

 

[Jez19844]

Just ordered this tray and thinking I'm likely to have the same issue. Does drilling the hole on the waste tube (presuming underside) mean I'll get sewer smells as breaching seal on the waste? Many thanks for this btw

 

[JohnOfChelmsford]

Just ordered this tray and thinking I'm likely to have the same issue. Does drilling the hole on the waste tube (presuming underside) mean I'll get sewer smells as breaching seal on the waste? Many thanks for this btw

Your mileage may vary, but I have noticed a faint smell but only some days. I would say get as much fall as you can to avoid needing the hole. I think I could put a one away valve on the easily accessible 40mm external waste before it joins the soil stack, but I'm waiting to see if wife or guest notice a smell as it's little and not often.

 

[Jez19844]

Thanks for the reply, one way valve seems like a good plan. Surprising mira would recommend something that breaches the seal. Saw another article where someone had drilled a load of holes in the actual tubes themselves, they seem to find that did the trick but can't see how it would help with air locks.