Unvented cylinder overflow pipe into soil stack?

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Hi all,

I've got an unsightly overflow pipe leading from my unvented cylinder and out of the house on my side access. Would it be a dumb move to have it plumbed into a soil stack instead? I asked a plumber in the past and he said it's important to know if the overflow pipe is running but right now I wouldn't be able to tell anyway as it's outside and rises a few inches of the ground.

Any thoughts would be appreciated.
 
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NOTE a plumber
just a DIYer / House holder

i would want to see the problem , in the past, i would know of the issue , until i saw the overflow leaking water
but right now I wouldn't be able to tell anyway as it's outside and rises a few inches of the ground.
do you have a photo , if its a Cylinder tank, why does it go underground and then rise UP ?

If it goes into a soil stack , then you would not know there was an ISSUE , and as you say, you would not know know anyway, and possibly if the overflow blocked then the house may get flooded causes a lot of damage.
If anything get it repositioned so you can see the problem

I had a Ballcock , in the loft , which did not switch off completely , and also a pressure vessel issue , where the pressure in CH was around 3 , again i would not know as its all in the loft , but noticed the leaking overflow pipes and able to resolve
 
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Sorry, I missed some vital info. The Unvented cylinder is now in the loft and I live in the 2 storey house. So the overflow/relief pipe drops down in the first floor, runs through the ceiling cavity and exits the building at first floor and is then plumbed down to ground floor level.

Does that help clarify my query a little?
 
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I think there may already be a tundish but it's in the loft, so unlikely that we'll know if it's running?

Fit a Hotun Detect.
https://hotun.co.uk/pressure-relief-valve-warning-now-has-audible-alerts/

hotun detect.JPG
 
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It is not an overflow!

It is probably an outlet for the temperature and pressure valve.

Since these can discharge boiling water there are strict regulations about where they can be discharged.
 
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It is not an overflow!

It is probably an outlet for the temperature and pressure valve.

Since these can discharge boiling water there are strict regulations about where they can be discharged.

Sorry you're absolutely right, it's a PRV!

Is there anything in the regs that state it cannot go into a soil stack?
 
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There are two possible discharge sources!

The temperature and pressure discharge with strict regulations!

A 6 bar plain PRV from the cold inlet to the cylinder. The discharge from that can go almost anywhere as it will always be cold.
 
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Note the pipework MUST be Polypropylene and use PP push fit fittings for their high temperature resistance.
All work to be done by a G3 qualified installer.
 
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All plastic that is part of the T&PRV must be high temp resistant (certain PP/PE/PVC-U) plastics. Not all waste/soil pipe is suitable as it won't take the heat if a T&PRV goes off dumping water @ >95deg.

You may find your soil pipe isn't suitable and can, in effect, melt. If both of the dump valves are tee'd into each other before the tundish, which a lot are , then the D2 run and downstream will need to be heat resistant.

Plastic Standards can be found here -
https://www.bpfpipesgroup.com/media/20922/Discharge-from-unvented-hot-water-storage-cylinders-into-plastic-sanitary-pipework-systems.pdf#:~:text=Given the high temperatures reached during valve operation,,be to connect to a soil pipe manifold.
 

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