Pressure Test Leakage 1

[Will007]

We are having problems with our ductile iron line/ HDPE line holding pressure.

The contractor says its an air lock problem, and we said its a water leaking somewhere.

We pressurized the waterline up to 125psi and 70 minutes later it dropped to 95psi.

Is there a way to know if this is a water leak or if it is an air lock issue.

Please advise.

Thanks

 

[PEDARRIN2]

Try a smoke test where the plumber/installer seals the piping and introduces a colored "smoke" into the sealed pipe.

If there is a leak, then you know it is not an air lock problem.

 

[bimr]

Here is a link to a training class for hydrostatic testing of water mains:

http://www.ohiowater.org/oawwa/Training/WDS Presentations/Hydrostatic Pressure%

 

[SteveWag]

If a fair amount of air is trapped in a high spot, some air will dissolve into the water because of the pressure. This will appear as a drop in pressure. The key is to measure the amount of water it takes to raise the pressure from 95 to 125 PSI. If this is done say three times and the same quantity is required each time, then it is a leak and you will observe that only a small quantity of water is required. But, if the quantity of water per trial steadily decreases, then it is air. You can measure the water by taking the suction of the test pump from a container and calculating the volumetric drawdown.
Steve

 

[cvg]

generally, if the pressure drops and then holds steady - probably air. If it drops and then continues to drop, you have a water leak.

 

[coloeng]

One thing that we have found when pressure testing HDPE is that the pipe will expand to a certain extent. We normally have to pump it up to the test pressure 3 to 4 times before it will be expanded to its fullest. Usually you will see the pressure drop after pumping it up the first time and then it won't drop quite as much each subsequent time.

Hope this helps.

 

[Maury]

Do what SteveWag suggested. Have the suction end of the pump draw from a barrel. Start the pump periodically over the test period to maintain the pressure and measure the volume of water lost from the barrel. This is the amount of leakage. The specifications should tell you the allowable leakage.

I'm not familiar with HDPE pipe, but with ductile iron I've seen the type of pressure loss you describe even though the leakage was barely measurable.

 

[PhxCivilPE]

A good contractor will place a tap or blowoff at the high end where air would normally be trapped. When the line was filled, they would be able to release the air at this point; thus avoiding any air issues.

Honestly, a good contractor wouldn't have a problem with their line.