Testing for back pressure with pressure washers

Testing For Back Pressure

To test for back pressure, remove unloader and flow switch (if installed) from pump outlet.

Connect pressure gauge (3000 PSI gauge is more accurate than 5000 or 6000 PSI) in between pump outlet and coil inlet with a test hose. The unit’s coil inlet hose can have a restriction and give incorrect testing pressure.

Disconnected outlet hose from coil, do not connect a gun to the outlet. Turn on unit, if there is scale build up inside the coil, it will show on the pressure gauge.

Generally if the back pressure is higher than 500 PSI, descale of the coil is recommended. The scale can continue to build up causing reduced heat of the water and outlet pressure. If the back pressure is over 1000 PSI, a coil replacement is recommended because if a descale in performed, the scale may not clear. Occasionally the heavier scale particles can release exposing a pinhole in the coil piping or weld and the coil will need to be replaced as a result.

Scale build up occurs when the heater is used and over time created deposits onto the piping wall. The quality on water being used can cause build up quickly.

Also have chemicals , such a degreasers, running through the coil and cause faster scaling. Example – a customer that has a PGHW with an attached floats had a employee added vent hood cleaning into the float tank, caused the unit to only have 1000 PSI outlet pressure. This new PGDC does not have this set up so this will need be an issue for him in the future.