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.
Best Answer
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.