G3 trap

[Pete]

My plumber mate who is helping me fit my ASHP reckons I need two traps for one pipe and I am not so sure. I have the relief valve for the cold and the blow off for the UVC going into a waste pipe. My mate reckons there should be a water less trap directly underneath the tundish, the 1 1/2 pipe then runs round to the 110mm pipe but I need to put in the drain for the steam oven so he said just put in another trap and connect the oven. 

My question is why cannot I not just have one trap directly of the 110mm stub pipe and then attach both the steam oven and UVC at their respective points? TIA

[PeterW]

Can’t have a shared trap under G3 regs, and it has to be of pipe suitable to take boiling water so beware that if your BCO is on the ball he could pick up that 110mm UPVC is not rated above 90°C...

 

I would branch the steam oven off the stack with a strap boss and just run a separate drain with another waterless trap. 

 

 

[Pete]

51 minutes ago, PeterW said:

Can’t have a shared trap under G3 regs, and it has to be of pipe suitable to take boiling water so beware that if your BCO is on the ball he could pick up that 110mm UPVC is not rated above 90°C...

 

I would branch the steam oven off the stack with a strap boss and just run a separate drain with another waterless trap. 

 

 

That's not good as I have no way of getting the blow off outside other than the 110mm drain. Thanks for the explanation but will have to just use the 110mm and see if he spots it

[joe90]

I had to run 22mm copper all the way to outside fir my G3.

[PeterW]

As long as the 40mm is done in something “heat proof” then you should be fine. Most don’t notice but some do ..!!

[LA3222]

@PeterW Will the 40mm high temp pipe going into a standard soil stack be ok if the soil stack is not high temp? I was looking at this the other day and found that doing the 40mm in a high temp plastic and using a Hep2O waterless waste seemed to be the solution. But the 110mm soil stack I have does not meet the high temp requirement, I spent ages scrutinising the BS no. for the Brett Martin stuff I used - annoying, as if I had pre-planned this I could  have used the right stuff for the whole drain run.

 

I'm now in two minds, run it into the main drain and hope it never pumps boiling water down there or run it through the wall.  I don't want to run it through the wall and I'm thinking that if an ASHP runs at 60 degrees, how can I get boiling water through it - surely the only issue would be pressure being exceeded leading to flow through the tundish rather than temperature? In which case, connecting the tundish to the soil stack should be ok?

[joe90]

3 minutes ago, LA3222 said:

ASHP runs at 60 degrees, how can I get boiling water

Immersion!

[Gone West]

1 hour ago, Pete said:

Thanks for the explanation but will have to just use the 110mm and see if he spots it

My BCO wasn't interested/didn't notice.

[PeterW]

Ok in this scenario @Peteis talking about stub stacks so I’m assuming 6-800mm of UPVC above the slab. Look at the regs for G3 and it tells you the minimum pipe before a bend and that’s the minimum you want before you go to something else. In reality it may not get checked but it’s not in line with G3 if this isn’t done correctly. 

[SuperJohnG]

So there is 110mm high temp soil pipe available?  

[LA3222]

44 minutes ago, SuperJohnG said:

So there is 110mm high temp soil pipe available?  

From building regs:

 

3.60 The discharge pipe should not be connected to a soil discharge stack unless it can be demonstrated that the soil discharge stack is capable of safely withstanding temperatures of the water discharged, in which case, it should:

 

I did start looking into this whilst looking at the tundish situation but stopped as it isn't something I can change now.  You can get underground soil pipes made out a different type of plastic which can withstand high temperatures.

 

I'm now resolved to connecting mine up and hoping it never turns into an issue.

[Russell griffiths]

If this is run in copper to outside, how do you finish it outside, and what should it drain into. 

[joe90]

Just now, Russell griffiths said:

If this is run in copper to outside, how do you finish it outside, and what should it drain into. 

Mine is run down to just above ground level (so it’s can’t scald anybody) above French drain .

[ProDave]

32 minutes ago, Russell griffiths said:

If this is run in copper to outside, how do you finish it outside, and what should it drain into. 

It must end at least 100mm above the ground and if in an accessible position should be covered with a cage.

 

 

I had to remove a few stones to lower the ground level a bit to get the 100mm

[Pete]

5 hours ago, joe90 said:

I had to run 22mm copper all the way to outside fir my G3.

Not helpful!!?

[Pete]

2 hours ago, LA3222 said:

From building regs:

 

3.60 The discharge pipe should not be connected to a soil discharge stack unless it can be demonstrated that the soil discharge stack is capable of safely withstanding temperatures of the water discharged, in which case, it should:

 

I did start looking into this whilst looking at the tundish situation but stopped as it isn't something I can change now.  You can get underground soil pipes made out a different type of plastic which can withstand high temperatures.

 

I'm now resolved to connecting mine up and hoping it never turns into an issue.

Same here!

[Oz07]

Does the length of the run allow water to cool down sufficiently to run into normal black soil then @PeterW?

 

Like a couple of m of 40mm then will it be cool enough not to melt the 110mm?

[Russell griffiths]

2 minutes ago, Oz07 said:

Does the length of the run allow water to cool down sufficiently to run into normal black soil then @PeterW?

 

Like a couple of m of 40mm then will it be cool enough not to melt the 110mm?

I was thinking the same, what is the max discharge temp, then what would that be 3-4 m away. 

[PeterW]

15 minutes ago, Oz07 said:

Does the length of the run allow water to cool down sufficiently to run into normal black soil then @PeterW?

 

Like a couple of m of 40mm then will it be cool enough not to melt the 110mm?

God knows I don’t write the rules but it’s in the G3 layouts - let me see if I can find it ..!

[PeterW]

 

This is the CIBSE spec - I’m just looking at the BRegs now. 

[PeterW]

You need to check the spec on the soil pipe as it needs to meet the standards above for either PE or UPVC. ABS isn’t allowed from memory, and solvent weld is not rated for 90°C. 

[LA3222]

1 hour ago, PeterW said:

 

This is the CIBSE spec - I’m just looking at the BRegs now. 

This is the drawing I was looking at which prompted me to check the EN type Brett Martin soil stack/underground drainage i had used.

 

Typical that the 'standard' one I used isn't suitable. So, now I weigh up poking a hole through my house in the off chance the TPRV triggers or, I run it to the soil stack and potentially trash all my foul drains?‍♂️

 

I suspect it would have to be discharging at high temps for a long time to do any real damage - so I'm gonna tap it into the soil stack!

[Pete]

1 hour ago, LA3222 said:

This is the drawing I was looking at which prompted me to check the EN type Brett Martin soil stack/underground drainage i had used.

 

Typical that the 'standard' one I used isn't suitable. So, now I weigh up poking a hole through my house in the off chance the TPRV triggers or, I run it to the soil stack and potentially trash all my foul drains?‍♂️

 

I suspect it would have to be discharging at high temps for a long time to do any real damage - so I'm gonna tap it into the soil stack!

Join the club. I am hopefully moving in soon so if anything bad happens you will the 3rd person to know after my wife and I (if I am still breathing)

[Oz07]

For peace of mind could the overflow on these not be configured to trigger a cold outlet somewhere. 

[LA3222]

1 hour ago, Oz07 said:

For peace of mind could the overflow on these not be configured to trigger a cold outlet somewhere. 

 

That would be a neat solution,  damned if I know how it could be done though.