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Drain air test questions


jamieled

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I have a couple of things to sort for my completion. One of them is to do with the air test. For reference, I laid and tested all the external 110mm soil piping, the groundworkers laid the soil piping through the founds (which I tested as they did it). I used a plumber to do all internal waste piping and plumbing stuff.

 

I have a single main stack which does most of our waste. I can plug it externally in an IC. I have an access cap on the stack internally from which I can attach my pressure gauge. I'm struggling to get the air test to hold. At the moment, the main reason seems to be that I can hear bubbling in the upstairs shower trap and occasionally in a downstairs sink trap.

 

Firstly, can someone confirm that the pressures I need to use for air testing the internal stack/traps are the same as the external soil pipe?

 

Secondly, if this is the case, how do I seal the traps for the air test? The plumber assures me he tested at first fix so I'm working on the basis that it's the traps rather than a problematic joint or pipe leak.  The shower trap looks to be a fairly standard job but it also looks rubbish from the point of getting a decent seal.

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Too late for OP but I prefer as i've laid drains extend all your pipes up by 1m. Bung them from the closest IC then fill up and leave while BCO visits for DPC. Discuss with him and get him to tick his box that drains are tested job done.

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1 hour ago, jamieled said:

Firstly, can someone confirm that the pressures I need to use for air testing the internal stack/traps are the same as the external soil pipe?

 

The regs say positive pressure of at least 38mm water gauge for at least 3 minutes.  For below ground pipework it is 100mm.

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You can never get the soil stack to hold more than the shallowest trap holds, plug the top of the svp and the manhole then push the manometer hose through a trap, WC is easiest blow in some air or water, the guage should stay at a positive pressure marked with a pencil after a few mins and not leak away to nothing 50mm of difference in level would be good but with shallow seal traps 38mm might be the best you will get 

 

 

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If the pressure in "mm of water" is greater than the depth of water in your trap you will get bubbling.

 

So have you got a very shallow trap in the shower? 

 

Have you fitted the innards if it's a top access trap?

 

Try topping them up with water slowly to making sure they are full of water before doing the test.

 

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21 minutes ago, Temp said:

So have you got a very shallow trap in the shower? 

 

Have you fitted the innards if it's a top access trap?

Yep, I reckon it is fairly shallow, though my earlier attempt at an air test was testing to get it to 100mm. It seems to hold at 40mm when full of water.

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