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Using 4 steel radiator like bands, I replaced a section of underground lawn sprinkler black plastic pipe that runs over a septic drain field. Repair couplers do not leak until i press my foot down on one of four running sprinkler heads. Is that normal? Would the leak have been due to the hair dryer i used to make the plastic pipe more pliable?

Hoping someone has tried the same stress test and would share their experience. I understand the physics of increasing the pressure by closing off an end. Hoping to get the perspective of lawn sprinkler experts as to whether these radiator hose couplings almost always leak a little when pressurized? I want to keep unnecessary water from getting into the septic drain field.

Water pressure where I live is 85psi, but noticed most water garden hose accessories sold locally are rated to only 60psi.

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    85 PSI? If your sprinkler system does not already include a pressure reducing valve (or regulator) it probably should...for garden hoses, there are regulators that screw onto the faucet available for $15 or less in fixed pressures such as 25 and 50 PSI.
    – Ecnerwal
    Commented May 22, 2015 at 2:30
  • The idea of pressure reduction is slow to get to these parts. Wish for the days when everything was overengineered and overbuilt.
    – rjt
    Commented May 22, 2015 at 2:39
  • As @asmyldof stated reduce the over all flow and the pressure increases thus the leak. For a simple field test of this loosen a hose that is running with no restriction until it starts to leak at the faucet then tighten slightly for no leak, now step on the hose it will leak because stepping on one sprinkler reduces the flow and increases the pressure thus the leak.
    – Ed Beal
    Commented Jun 8, 2018 at 5:32
  • Yes, i understand increased pressure from sealing off faucets. My question is simply “Is it normal for these hose repairs to leak?”
    – rjt
    Commented Jun 11, 2018 at 17:59

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The pressure in the tubing will be lower if there is an open-end or slightly-open-end. If the supplying valve is a normal tap (i.e. not a ball valve) that pressure is even lower, because usually the center hole of the tap is smaller than the outgoing tubing.

When you close the hole, the pressure increases measurably, because the outflow that mitigated the pressure has stopped and now the full main pressure can be applied to the tube's walls and couplings.

Now if the couplings or tube has a tiny hole, that can mean it leaks only when the end of the tube is closed.

Imagine having a 0.1" (2.54mm) hole and a chunk of clay. If you gently push the clay against the hole, nothing goes through. If you put your weight on it, you will get the clay through quite quickly. In very small openings the water can act exactly as the clay, too low pressure and it will not want to go through the hole, but rather out the sprinkler. Too much pressure and it will squirt out, because it has nowhere else to go.

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  • There are still at least 3 other sprinkler heads letting the pressure off, so surprised the repairs leaked.
    – rjt
    Commented May 22, 2015 at 1:27
  • It's down to resistance of flow. Any minor difference can be the straw that breaks the sprinkler's back, but for a deeper analysis you will need to give deeper information. Lengths, couplings, junction points, tap type, the works.
    – Asmyldof
    Commented May 22, 2015 at 1:34
  • I was not really looking for theory as much as practical field test experience. I was wondering if others happened to stress test their repairs this way. Will post some more pics and details after sun comes up.
    – rjt
    Commented May 22, 2015 at 2:41
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If the repair "band" are the same as wormdriven hose clamps than you can tighten them until repair doesn't leak. From your description of the irrigation line I see it as that black, 1/2 inch pipe that uses compression fittings and 1/4 inch barbed tubing?

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  • Yes, radiator worm-driven hose clamps tightened with a socket driver or screwdriver. One inch black and some places blue irrigation pipe. I had tightened them as much as possible. It was cold, so tightening under a little heat could have possibly helped.
    – rjt
    Commented Jun 11, 2018 at 18:03
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Local irrigation expert do not use the worm-driven radiator hose clamps, but solid metal bands that they crimp with a 18” to two foot tool.

Would be interested if lower water pressure ( 60psi or less) localities do not find a need for the ring clamps and still use radiator clamps.

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