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Discuss 0.5mb drop on tightness test - Should I be worried? in the Plumbing Jobs | The Job-board area at Plumbers Forums

they would say its within safe limits why did you go looking for the leak when you didnt need too
Agreed, there almost certainly isn't a leak, and none within the meaning of the regs. No system would be totally leak free - if you left it for a year the pressure would fall. As others have said, change of temperature could easily cause that sort of pressure change. A fall of about 0.15°C is all it needs for the pressure to fall by 0.5mb.
 
we don’t use steel for gas pipes in domestic properties. The permissible drop is to cater for old gas valves on appliances, pipework only has to be totally tight.
How come, I come across quite often steel gas pipes which are either under the floor connected to copper or bedded in concrete? However, the point I made is to check for weaknesses and cracks which could be hidden due to slag or other debris.
 

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How come, I come across quite often steel gas pipes which are either under the floor connected to copper or bedded in concrete? However, the point I made is to check for weaknesses and cracks which could be hidden due to slag or other debris.

you test at op and thats it
 
A domestic gas installation should be tested at 1 bar for 30 mins ?
Standing pressure is usually well below 30mbar and working pressure 21 +\-2 so probably a bit overkill.
I do agree with zero tolerance though, that’s alway what I aim for anyway even if it’s within permissible drop.
Overkill ? Sorry mate but I disagree with that term. A gas pipe should be tested with a lot higher pressure than just 30mbar. You have to check the pipe under a load test which means with higher pressure than the one you will have when the pipe is in use. You will test the material and joints for weaknesses , hairline cracks or pinholes which are covered by slag. Due to the higher pressure you make sure to find those weaknesses or cracks which you won’t find by mbar.
 
Overkill ? Sorry mate but I disagree with that term. A gas pipe should be tested with a lot higher pressure than just 30mbar. You have to check the pipe under a load test which means with higher pressure than the one you will have when the pipe is in use. You will test the material and joints for weaknesses , hairline cracks or pinholes which are covered by slag. Due to the higher pressure you make sure to find those weaknesses or cracks which you won’t find by mbar.

so do you remove the boiler cooker and fires to do the test as these can only take 20 mbar
 
You dont need to do a TT on a service
Unless you
Overkill ? Sorry mate but I disagree with that term. A gas pipe should be tested with a lot higher pressure than just 30mbar. You have to check the pipe under a load test which means with higher pressure than the one you will have when the pipe is in use. You will test the material and joints for weaknesses , hairline cracks or pinholes which are covered by slag. Due to the higher pressure you make sure to find those weaknesses or cracks which you won’t find by mbar.
But the pressure in the pipe is in mbar, we’re only talking about domestic installation pipework with a working pressure of 19-23 mbar and standing pressure usually a few mbar higher than that so why the need to test to 1 bar?
 
so do you remove the boiler cooker and fires to do the test as these can only take 20 mbar
Yes, you would need to otherwise you will ruin the appliances. You can only test them via there operating pressure as you know. But when it comes to testing the pipework throughout the property when installed new then you will need to use the appropriate fittings to cap them off and test them with higher pressure ( but that’s the way we do it in Germany ). We do 2 test before bedding pipes into the concrete, load testing ( 1bar with air or N ) for 30min -1hour and then a 15 min test leak test.

Sorry but it is difficult to explain german terms in English. I think you can’t be careful enough when it comes to gas. I know it’s done differently here and I do whatever is required but I would wish few things would be different.
 
Unless you

But the pressure in the pipe is in mbar, we’re only talking about domestic installation pipework with a working pressure of 19-23 mbar and standing pressure usually a few mbar higher than that so why the need to test to 1 bar?
If I can decipher his posts, I think the gas pipework in his home country is welded and welded joints can be terrible, so it makes sense to test at much higher pressure
 
Unless you

But the pressure in the pipe is in mbar, we’re only talking about domestic installation pipework with a working pressure of 19-23 mbar and standing pressure usually a few mbar higher than that so why the need to test to 1 bar?
We have also 18-25mbar but when it comes to test pipework we have to undertake those tests and get that printed off with a special machine.
 

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