Shurflo Trail King 30psi pump repair


Full Member
While away in France our pump started cycling and pulsing, never used an accumulator before and never had the pump
Pulsate. As the water still flowed well when the shower or sink tap largely full open I left it till we got home.
On removing the pump housing from the motor and inspecting the seals and diaphragm's I noticed quite a lot of browning
Stain but not anything that would cause it to pulse at the tap set at low flow. I then took the pressure switch housing off the pump housing and found the culprit after a little studying of it's operation.
In the diaphragm housing there is a rubber washer attached to a plunger then a fairly light spring which pushes against a plastic cup affair, which sits in a circular cut out on top of this is a silicone rubber gasket all this is held in place by the pressure switch housing.
When the tap is turned on the pressure that has been built up in the water system drops so that the plunger which had previously been pushed up by the water pressure lifting the plastic cup in its circular housing and silicone gasket hence pushing against the micro pressure switch and breaking the power circuit stopping the pump now the pressure has dropped it brings power back into the circuit and the pump starts up.
What i discovered was the plastic cup was sticking in its circular cut out and was not moving freely so that it did not matter where the setting screw was the pump would only work when the pressure in the system was right down low and only switched off with the sudden release off the little plastic cup when the water pressure built up enough to make it move, therefore when the tap was only partly open there would be a pulsing sensation instead of a steady flow of water where the pump pumps for 5 seconds turns off for 2 or 3 seconds then pumps again for 5 seconds and so on. The solution was to rub the edge of the plastic cup with 1200 wet and dry give it a light coat of silicone grease so that it sat smoothly and moved freely in its housing and put it all back together. Hey presto! Back to its old self no pulsing and the wife can again save water by only opening the sink tap at a dribble to rinse the utensils 😄👍.Phil

Millie Master

Full Member
Brilliant Phil, thanks for posting this info.

My pump isn't quite as bad as yours was but now I know what to do with the otherwise excellent pump.


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