Maximum permissible soil pipe length and number of bends?

[RrogerD]

Hi,

I am new to posting here so please bear with me.

Fabulous forum. I have learnt so very much over the years reading as a guest. Thanks to everyone for their contributions.

I am planning the creation and installation of two new bathrooms on a 1st and 2nd floor. The WCs will be sited at the far corner of the property from the existing soil stack.

I am aware that Building Control will be able to set me right but, I want to have all of my decisions made if possible, before getting them involved.

My questions are, what is the maximum number of bends permissible and, what are the maximum pipe lengths allowed, if vented?

I have attached a rough sketch showing layout and dimensions, which may help.

Thanks in advance.

Untitled

• RrogerD
• 8 Jun 2013
• 2

 

[^woody^]

You can't bend a stack like that, and it needs to go vertically and connect to a drain via a rest bend

 

[RrogerD]

Hi Woody,

Thank you for taking the time to reply.

Can you possibly expand upon your comments for me.

The 'bends' in the new stack are needed because the drop from 1st and 2nd floor WCs is unterupted by a hallway. The 1.13m turn, directs the waste across the hall ceiling and into the adjacent lounge whereby it then drops the 2m or so into the basement. it then traverses across basement ceiling and then into the exiting stack and into the ground.

Would increasing the gradients ensure a clear flow?

What would be your solution instead?

What do you mean by a 'rest bend' connection?

Many thanks once again for your time.

 

[noseall]

You can bend the stack provided you have access hatches on the bends.

 

[^woody^]

Its not so much about access at the potential block points, but more to do with siphonage, and pressure on joints

Part H discourages it and IIRC, non of the suppliers will recommend it without them designing it

And a SVP needs to go to its own drain not to another SVP

A rest bend, AKA "long radius bend", is a special bend designed to go at the base of a SVP, to allow smooth discharge of the effluent

 

[noseall]

I viewed the post on my phone and thought it was going into a horizontal line.

Hmm odd arrangement?

 

[RrogerD]

Hi Woody and noseall,

Thanks again for the replies. I did try and have a read through Part H, but could not really find out what I was after.

Unfortunately, the property arrangement and floor layout does not allow for many alternative options.

If you have any other thoughts, that'd be great.

Cheers

 

[jeds]

Your layout isn't impossible. BSEN 12056 says offset bends in the discharge stack should be avoided - it doesn't say they're not allowed. The radius of the bends should be twice the diameter - i.e. 200mm.

 

[ivixor]

Might be easier to go down into the ground and install a proper underground restbend, connecting to wherever the existing vent pipe drains to. Would also look a lot nicer than a big diagonal soil pipe across the house.

 

[RrogerD]

Hi,

Many BIG thanks to you all in taking the time to reply. Thank you.

I have now had a visit from the BCO and they have OKed my suggestion. I am getting them to put in writing of course.

Also, just spoken to another plumber on site who said that as being a terrace and the existing pipe being the only option of exiting the building, there was little else that could be done. There are no visible manholes or space to instal a new one, anywhere near.

The 'diagonal across the house' is in the unused basement, so not an issue.

Thanks again.

RrogerD