Bathroom waste arrangement and boiler condensate drainage

[Allthegearnoidea]

Hello All!

 

We have a ground floor extension underway, and I need to get the drainage from the existing upstairs bathroom sorted before the roof can go on.

We're adding a new W/C downstairs which has necessitated moving the soil stack over a few meters. (The underground drainage is already in place and signed off by building control with the upstairs W/C connected temporarily.)

Moving the soil stack leaves me with the problem that the bath waste is now more than 4m away. I understand the max run for 40mm waste is up to 3m, and 50mm is up to 4m.

This is what I have in mind.

Blue = 40mm bath waste
Green = 32mm basin waste
Red = 110mm

I was thinking it would be sensible to put rodding points in at A & B (with inspection covers internally).

I'm planning to use one of these (or similar) for the 40mm to 110mm connection.

 

 

 

 

Here's the house / extension in profile, so you can see that most of this pipework will be boxed in internally.

 

So you can see the full picture, this is the arrangement of the upstairs W/C, showing what it would look like if 40mm pipe was used for the full run.
 

The last diagram also shows the boiler condensate which I need to re-route into the bath waste. I plan to get this particular bit done by a Gas Safe registered plumber, but I'd still like to have a vague understanding of what needs to happen here so I can plan the other pipework accordingly - I'm not sure it's quite as simple as plumbing the condensate drain into a tee below the bath.

Does the arrangement look OK (ie., compliant with building regs), and does anyone have any clues on what needs to happen to plumb the condensate drain into the bath waste?

Thank you for any advice!

 

 

 

[Redbeard]

I may have misunderstood, but if 40mm is limited to 3m, how is your 4.5m run (with a 90 deg bend in) OK? And is the length limitation about potential siphoning, or about the need for a rodding eye? If the latter then I can see how you could 'engineer' a rodding eye at the 90 deg bend so that it truly is 3.1m and 1.4m, but if it's about potential siphoning then you still have at least a theoretical problem...? Can you clarify?

[Allthegearnoidea]

10 minutes ago, Redbeard said:

I may have misunderstood, but if 40mm is limited to 3m, how is your 4.5m run (with a 90 deg bend in) OK? And is the length limitation about potential siphoning, or about the need for a rodding eye? If the latter then I can see how you could 'engineer' a rodding eye at the 90 deg bend so that it truly is 3.1m and 1.4m, but if it's about potential siphoning then you still have at least a theoretical problem...? Can you clarify?

 

Sorry, I've just realised that isn't too clear.  

 

This is what it would look like from inside the bathroom, so under 3m of 40mm from the bath. I'm just unsure about the transition into the 110mm, as I haven't seen it done this way before...

 

[MPx]

I suspect you'll get horrible gurgling in the bath and sink if there's no air admittance valve upstream of the basin.  Otherwise generally "better" to drop into the main sewer from the top rather than end (cap the end for rodding) - but you may not have enough fall available for that at the moment, and what you have in mind will work.

[Allthegearnoidea]

14 minutes ago, MPx said:

I suspect you'll get horrible gurgling in the bath and sink if there's no air admittance valve upstream of the basin.  Otherwise generally "better" to drop into the main sewer from the top rather than end (cap the end for rodding) - but you may not have enough fall available for that at the moment, and what you have in mind will work.

 

Would one of these fitted to the basin help?  Or do you think I would still have the same problem with the bath?  

 

[Allthegearnoidea]

Or I could try to get an AAV in here (in orange)...but it would be tough to get it above the basin trap height.

 

[Nickfromwales]

The pipe off the 110mm should be 50mm up to where it heads in to the bath, turning in on a T with a rodding access (cleaning eye) for maintenance.

 

From the 50mm T you reduce to 40mm to get to the bath T, and then the 40mm pipe continues to the boiler. 
 

That then terminates at a 40mm T with the centre of the T having a 40 > 21.5mm reducer in it for the boiler condensate, and a 40mm air admittance valve to complete the run.

 

Absolutely ZERO need for a GSR plumber, this will just add wasted expense.

[Allthegearnoidea]

2 hours ago, Nickfromwales said:

The pipe off the 110mm should be 50mm up to where it heads in to the bath, turning in on a T with a rodding access (cleaning eye) for maintenance.

 

From the 50mm T you reduce to 40mm to get to the bath T, and then the 40mm pipe continues to the boiler. 
 

That then terminates at a 40mm T with the centre of the T having a 40 > 21.5mm reducer in it for the boiler condensate, and a 40mm air admittance valve to complete the run.

 

Absolutely ZERO need for a GSR plumber, this will just add wasted expense.

 

Thank you Nick!

 

Just to confirm - is this roughly correct?

 

Red = 110mm

Grey = 50mm

Green = 32mm

Blue = 40mm

Yellow = 21.5mm

 

 

 

On the other side of the wall, is this what you mean?

 

One of the reasons I was going to get a plumber in for this was the mention of a trap in Approved Document H...is this necessary?

 

 

 

 

[Nickfromwales]

Boilers usually have the trap inbuilt . I’ve fitted more gas boilers than I care to remember, and we’ve never had to fit a 3rd party trap. 
 

And yes, your pic is spot on. 

[Allthegearnoidea]

10 hours ago, Nickfromwales said:

Boilers usually have the trap inbuilt . I’ve fitted more gas boilers than I care to remember, and we’ve never had to fit a 3rd party trap. 
 

And yes, your pic is spot on. 

 

Thanks again!   Have confirmed the Gloworm boiler we have is fitted with an inbuilt trap 👍

 

Is this the best way to orient the blanking cap for rodding?  Looking at it I feel like I should turn it through 90° so debris doesn't collect...

 

 

 

And...hopefully last question - can the AAV go at any height as long as it's more than 200mm above the highest water inlet?

[Nickfromwales]

27 minutes ago, Allthegearnoidea said:

 

Thanks again!   Have confirmed the Gloworm boiler we have is fitted with an inbuilt trap 👍

 

Is this the best way to orient the blanking cap for rodding?  Looking at it I feel like I should turn it through 90° so debris doesn't collect...

 

 

 

And...hopefully last question - can the AAV go at any height as long as it's more than 200mm above the highest water inlet?

You can turn the T and still get a thin rod up to the bath, so no worries there.

 

Water will come out of the WC pan before it gets anywhere near that high, but rule of thumb is as you show. 200mm is plenty, but you can go higher, just no point afaic. 

[Allthegearnoidea]

24 minutes ago, Nickfromwales said:

You can turn the T and still get a thin rod up to the bath, so no worries there.

 

Water will come out of the WC pan before it gets anywhere near that high, but rule of thumb is as you show. 200mm is plenty, but you can go higher, just no point afaic. 

 

Great, I have a plan now - thanks again 👍

[Allthegearnoidea]

Right, I've made it to the outside and need to figure out the arrangement here...

 

Hopefully it's clear that the original / temporary stack is to be removed and the new stack is going over to the right. 

 

Option A - I personally prefer this because it gives me a sharp drop immediately after the WC outlet - similar to the way it was installed originally which has always worked very well.

 

 

Its a bit lower, but still around 2.4m at the join to the new stack

 

Option B - seems more conventional, about 200mm higher.  Might end up having to use a strap boss for the 50mm pipe at the stack which I don't really like. 

 

 

What's the preferred way to do this, and whereabouts are inspection / access covers recommended?  

 

Pipework all to be boxed internally:

 

 

Edited 9 hours ago by Allthegearnoidea

[Allthegearnoidea]

Option C - Previously the basin and bath went into a hopper where you can see the two temporary downpipes, these are currently just feeding into the old drain which is still there below the slab and working - ie., A & B join up underground anyway.  Reading the regs again, it does say that boiler condensate should be downstream of a sink (basin?), so maybe it's best to use this and box it in after all?  It would still be vented at the boiler end.

 

 

 

Edited 4 hours ago by Allthegearnoidea