Min. fall for shower waste not acheivable

[davphi338]

Hi,

I am having my soil stack moved as part of an extension. The builders have noticed that the shower waste will not have the min 1 in 40 slope if the waste is routed through the roof void as planned. They have suggested dropping the waste into the extension and boxing it in, either that or ripping up my shower tray and raising it by about 4 ins.

Anyone have any thoughts or suggestions that would enable me to avoid having to route the waste through the actual room. All the other wastes, toilet, sink and bath are OK because they exit higher than the shower waste.

 

[swidders]

Pump the water out http://www.dry-deck.co.uk/

 

[Bahco]

Easiest and cheaper to raise the shower tray. Look in the Faqs.

 

[davphi338]

looking at the buidling regs I can't find any mention of max waste length into a ventilated soil stack only for unventilated soil stacks. I take it a normal outside soil stack is ventilated or am I missing something. (Don't say brain, I already know that !!)

 

[swidders]

looking at the buidling regs I can't find any mention of max waste length into a ventilated soil stack only for unventilated soil stacks. I take it a normal outside soil stack is ventilated or am I missing something. (Don't say brain, I already know that !!)

I thought you were talking about having room for a 1:40 slope, not about lengths of pipe.

 

[davphi338]

I was, thats the issue the builders picked up.

However, I was reading the building regs for drainage and it kept mentioning max. waste lenghts. My shower waste pipe is going to be a total of approx 8m from the trap to the the proposed new position of the soil stack. I'm just hoping this isn't going to be an issue as well when the BCO calls.

 

[swidders]

Maximum lengths are 40mm- 3m, 50mm - 4m, 100mm - 6m, all requiring a minimum fall of 18mm per metre

 

[davphi338]

Thats what I've read in the regs but it seems those figures are for a non ventilated stack. It mentions a branch ventilation pipe or air admittance valve should be used if these distances are exceeded but doesn't give any max. distances for a ventilated system.

 

[swidders]

The figures are for ventilated stacks.

The books I'm looking at indicate the use of air admittance valves into the run to create a ventilated discharge branch system, but I can't find spacing so would assume the figures as previously indicated. BCO should be able to advise -they're doing b*gger all else for their money!

 

[sooey]

Thats what I've read in the regs but it seems those figures are for a non ventilated stack. It mentions a branch ventilation pipe or air admittance valve should be used if these distances are exceeded but doesn't give any max. distances for a ventilated system.

As swidders said, they're for a ventilated stack. The idea of using abranch ventilation or air admittance valve (anti vac trap) is to stop the trap from being sucked out if the waste water runs full bore in the overlong waste pipe.

 

[swidders]

Thats what I've read in the regs but it seems those figures are for a non ventilated stack. It mentions a branch ventilation pipe or air admittance valve should be used if these distances are exceeded but doesn't give any max. distances for a ventilated system.

As swidders said, they're for a ventilated stack. The idea of using abranch ventilation or air admittance valve (anti vac trap) is to stop the trap from being sucked out if the waste water runs full bore in the overlong waste pipe.

Twice in agreement!

From what I can gather in my extensive library (B&Q guide to insulation ), if you use a vent pipe on your 8m run, it should be
1/. minimum of 25mm diameter
2/. placed so that is is a maximum of 30mm from the (shower) trap
3/. joined to the discharge stack at above the spill-over level of the highest fitting serviced.

 

[davphi338]

Yes it seems I was getting confused between a ventilated stack and a ventilated branch system. So it looks like not having a fall of 1:40 is the least of my problems. I am going to have issues of the shower waste pipe being too long if I move the soil stack.

 

[davphi338]

sooey, is an air admittance valve the same as anti vac trap. If so would it be possible to simply replace the shower trap with an anti vac trap. It does say in the regs that if the lengths mentiond are exceeded a air admittance valve should be used or a ventilated branch system as per swidders description.

Ignore the above, reading it again it seems the only way to exceed the stated lengths of waste pipe is to have a ventilated branch system that vents into a vented stack or an air admittance valve stack.

 

[sooey]

sooey, is an air admittance valve the same as anti vac trap. If so would it be possible to simply replace the shower trap with an anti vac trap.

Sort of, but I wouldn't want to run an 8 metre shower waste with minimal fall. You'll end up standing in a tray full of water, especially so if you've got a powerful shower.

 

[davphi338]

I've now found this information that states that there is no max. for shower and bath waste lenghts. All too confusing really. I'll let the BCO decide.

http://www.mcalpineplumbing.com/wastetrapsandpipes.asp#pipe