Long waste pipe runs

[StormyK]

I want to install a new shower in a bedroom. However, whilst the waste pipe run is straight (apart from bends to join to soil stack & shower tray), it is 8 metres away. I intend to use a HepVo antisiphonic trap at the shower.

Having looked at the Building regs, I am a little confused as to whether 8 metres is too long and also what the issues are ie pipe capacity to drain the shower sufficiently quickly or foul smells (or some other reason). Building regs for unvented branch connections state a maximum 4m for a 50mm pipe. However, as I am using a HepVo trap, I assume that this requirement is no longer applicable (now vented) and I can't find any Building Regs info on maximum pipe lengths for vented waste pipes.

I can get a (gradual) vertical drop of at least 200mm so I can easily achieve the required gradient of 1.8 to 9mm/m. I intend to use a 40mm waste but could use a 50mm waste if required.

Can anybody advise as to whether the above will work? I do have the alternative of installing a Sanishower macerator but don't really want to do this unless there is no alternative.

 

[Bahco]

Use an antisyphonic trap and run the waste in 50 mm to be safe with a drop of 1 in 40 and you should be fine.
There is not much chance of you losing trap seal due to the speed (of the water) and the large area that is being drained. 40mm would probably be ample,

 

[StormyK]

Thanks. Much appreciated. As a matter of interest, what is the issue (foul smells, drainage capacity or other)

 

[Bahco]

The issue is loss of trap seal so allowing nice aromas from the sewers entering your bedroom, and of course complete drainage.
The speed at which your shower tray will drain determines the size of waste pipe. Max length is 3 metres on 40mm pipe which is why I advised you to use 50mm, (but still think 40mm is ample as I have done it myself).
If BCOs are involved they may ask you to fit air admitance valves.
Good luck

 

[kevplumb]

dont do it in pushfit use solvent

 

[StormyK]

The issue is loss of trap seal so allowing nice aromas from the sewers entering your bedroom, and of course complete drainage.
The speed at which your shower tray will drain determines the size of waste pipe. Max length is 3 metres on 40mm pipe which is why I advised you to use 50mm, (but still think 40mm is ample as I have done it myself).
If BCOs are involved they may ask you to fit air admitance valves.
Good luck

I thought that using a HepVo antisiphonic trap also eliminated the need to fit air admitance valves?

Quote from HepVo info
"HepVo actively eliminates negative pressure within the waste system by opening and allowing in fresh air until a state of equilibrium
with atmosphere is reached. This means that venting of the waste system, or the inclusion of air admittance valves in the waste system is no
longer necessary."

Also, can you comment on my next post re Washing machine (although I suspect I'll get a similar answer to this. Many thanks.

 

[Bahco]

Because your run is 8 metres BCOs may ask you to fit aavs. If they are not involved, as before.
I have been advised that the fall should be 1 in 50 for 50mm