Pressure testing - losing pressure, but no waters leaks?

[OGBUzzard]

Hi, I am testing a 1st fixer's copper pipework on a big job, I have connected the Boosted Cold, Hot, and Mains cold together and pumped up the pressure to 7bar. Over a matter of hours I'm getting a drop of about .2 bar. I can't find any signs of water leakage. This has happened before on a job I finished 3 years ago and haven't had any callbacks from that so I'm wondering is it just compression? are there any tips anyone has about pressure testing because it seems to be an inexact science to me, I have never had a test that stays at the same pressure over 24hrs and I have also never had leaks on these systems, however this is a much bigger job in a very expensive house and I don't want to be the cause of ceilings being ripped down etc to find a leak in the future. I know when you're doing a gas tightness test you are allowed a certain amount of pressure loss over a short period of time (minutes), is it the same with water??

 

[jtsplumbing]

Have you bled all the air B4 testing ??

 

[mike-c]

Are you using water or air to pressurise?
What are you using to cap off the pipe ends?
If it is air and you are using push fit stop ends they could be passing air as they usually need to be pushed back down after pressure has been introduced. You could spray them with ldf to see if they are passing.

 

[AlexGas]

From BS 6700:

Design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages – Specification

6.1.12.3.3 Testing of installations within buildings

The installation shall be filled slowly with drinking water to allow air tobe expelled from the system. The complete installation shall be inspected for leaks. The installation shall be tested hydraulically by subjecting the pipes, pipe fittings and connected appliances to a testpressure of not less than 1.5 times the maximum working pressure in accordance with clauses 6.1.12.3.4 or 6.1.12.3.5, depending on the materials from which the pipeline is constructed. There shall be no visible leakage of water and the pressure shall be maintained for one hour.

6.1.12.3.4 Test procedure for rigid pipes

The pipework shall be vented, filled slowly with drinking water and subjected to the required test pressure. Where there are significant differences (>10 °C) between the ambient temperature and the water temperature, there is an initial period of 30 min before the commencement of the test period, to permit temperature equilibrium after the test pressure has been applied. There shall be no visible leakage of water and the pressure shall be maintained for a test period of one hour.

Hope it helps.

 

[on31ll]

your testing with air i take it ? it may be down to temperature mate your reading will vary when you go back to read the gauge and its warmer or colder etc.

 

[OGBUzzard]

From BS 6700:

Design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages – Specification

6.1.12.3.3 Testing of installations within buildings

The installation shall be filled slowly with drinking water to allow air tobe expelled from the system. The complete installation shall be inspected for leaks. The installation shall be tested hydraulically by subjecting the pipes, pipe fittings and connected appliances to a testpressure of not less than 1.5 times the maximum working pressure in accordance with clauses 6.1.12.3.4 or 6.1.12.3.5, depending on the materials from which the pipeline is constructed. There shall be no visible leakage of water and the pressure shall be maintained for one hour.

6.1.12.3.4 Test procedure for rigid pipes

The pipework shall be vented, filled slowly with drinking water and subjected to the required test pressure. Where there are significant differences (>10 °C) between the ambient temperature and the water temperature, there is an initial period of 30 min before the commencement of the test period, to permit temperature equilibrium after the test pressure has been applied. There shall be no visible leakage of water and the pressure shall be maintained for a test period of one hour.

Hope it helps.

awesome reply, thanks mate, so it only has to hold at the same pressure for 1 bar....

 

[OGBUzzard]

NO, I am testing with water, air tests never give me any peace of mind..and I am using gate valses/ service valves which are all shut off fully, no push-fit stoppers.

 

[AlexGas]

so it only has to hold at the same pressure for 1 bar....

...1 bar!? You mean - 1 hour.

 

[ecowarm]

NO, I am testing with water, air tests never give me any peace of mind..and I am using gate valses/ service valves which are all shut off fully, no push-fit stoppers.

Service valve/ gate valves need to be capped as well OGBUzzard, gate vales are not designed to hold that pressure. Also as said Temperature can have a big effect on pressure

 

[OGBUzzard]

when you say they are not designed to hold that pressure, surely that's incorrect? the pressure in the house with the new main will be 7 bar, which is why we are testing everything back to the main at 7 bar.... just checked the wras website and lo and behold 10 bar is what an isolator can take, as I thought, and I won't bother checking for lever valves, sorry I think I said gate valves above, that was a mistake, I'm a bit tired!!. Besides if they couldn't hold the pressure they would be leaking, and the valves are all dry as a bone. Anyway I think after 7 years of fumbling around in the dark, some light has been shed and I'm more confident there aren't any leaks seeing as the test period is only an hour. I'm sure it'll pass that tomorrow. Thanks all

 

[OGBUzzard]

...1 bar!? You mean - 1 hour.

yes that's what I meant! sorry, exhausted...

 

[OGBUzzard]

we are filling the system with pretty cold mains water, and the heating is on in the house so I think this 30 minute acclimatisation period is where we are getting the difference, but if the water is getting warmer in the pipes surely the pressure should increase as the heat does??? (Source: GCSE Physics!)

 

[Gray0689]

If testing a first fix using water the pressure will always drop a bit .2 bar is nothing

 

[ecowarm]

when you say they are not designed to hold that pressure, surely that's incorrect? the pressure in the house with the new main will be 7 bar, which is why we are testing everything back to the main at 7 bar.... just checked the wras website and lo and behold 10 bar is what an isolator can take, as I thought, and I won't bother checking for lever valves, sorry I think I said gate valves above, that was a mistake, I'm a bit tired!!. Besides if they couldn't hold the pressure they would be leaking, and the valves are all dry as a bone. Anyway I think after 7 years of fumbling around in the dark, some light has been shed and I'm more confident there aren't any leaks seeing as the test period is only an hour. I'm sure it'll pass that tomorrow. Thanks all

Incoming main is 7Bar I would recommend a Pressure reducing valve with balanced supplies @ 3 bar, or you need to test @ 7 x 1.5 = 10.5 bar

 

[cr0ft]

If you had even a slight drip on a domestic system pressurised to 7 bar the pressure would drop much more significantly over an hour. I wouldn't worry about it.

 

[AlexGas]

If you are fitting the PRV at 3 bar - During the test pressurise the system to 4.5 bar

 

[Howsie]

Don't forget that the copper will expand with heat so that may account for it depending on what time of day you are performing the test.