Main line pressure testing?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by JimLS, Jun 30, 2010.

  1. JimLS

    JimLS New Member

    Jun 26, 2010
    I suspect I have a very slow main line leak but only when the line pressure is high. This is a 500 ft line from the water meter to the house. Pressure runs about 70 PSI normally. Is there a standard way to test this other than just watching to see if the meter moves? I know they use air for low pressure testing of drain lines but air pressure is not recommended for PVC. All the PVC is buried so there isn't a danger of flying plastic bits - I think this is the main reason for not using air pressure in PVC lines. Can I do this with air? Long ago I worked briefly in a calibration lab that had hand operated, positive displacement liquid pumps to put pressure on gauges for calibration. They looked a little like a grease gun. Is there some similar thing for applying liquid high pressure to water lines for testing? What pressure is used when testing pressure lines?

    I am thinking I could shut off the line at the meter and add additional pressure from the house side to test. For the extra pressure I could use an oil-less air compressor or perhaps rig up a PVC telescopic repair coupling and C-clamp or arbor press as a positive displacement pump.

    I am thinking there must be an industry standard way to test water lines and want to know more about how it is done.
  2. Doherty Plumbing

    Doherty Plumbing Journeyman & Gas Fitter

    Jun 22, 2009
    Red Seal Journeyman Plumber & Licensed Gas Fitter
    Penticton, BC
    There is a very easy way with water to check for leaks.... use a pressure guage.

    You'd need to install the guage so that it's between the curbstop at the road and the main shut off valve coming into your house.

    Fill the line up till you get X psi and then shut off the main valve going into the house so that the street is still keeping the line pressurized. Then kill the water at the curbstop and watch the guage.

    As I'm sure you know water isn't compressible so if you have a leak you'll lose PSI rather quickly.

    Professionals around here would use a hydrostatic pump to boost the pressure in the line to 200 psi (but NOT with PVC.....) but this is done upon installation to make sure the water lines are going to beable to hold the MAX pressure they'll ever possibly see.

    For someone just wanting to check to see if they have a leak they just need to see if they lose pressure. You could start with 30 psi and easily see if you have a leak within seconds of killing the incoming water from the street.

    On a side note I would NEVER pressure test PVC with air.
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