Adjusting and Troubleshooting the Pressure Switch
of your Water Pump

Pressure switches play an important role on board. They make sure that whenever you want water, you will get it.

As long as they do their job, fantastic. We forget about them...

Then comes the moment you just soaped yourself in under the shower and... there you go. A few pathetic drips are hanging out of the shower head...

This was the moment I decided to write this article, so you know what to do in order to finish your shower!


Pressure Switch

How do they work?

Connected to the fresh water pump, they sense the pressure of the water citcuit.

When you open a tap, the pressure will drop and the pressure switch will feel this.

Through a mechanical system, the electrical system closes which in turn activates the fresh water pump.

When you close the tap, the pressure will rise again until the set pressure is reached.

Now, you can adjust those 2 pressures.

The cut-in pressure is the lowest pressure at which the fresh water pump needs to start pumping. 

The cut-out pressure is the highest pressure at which the pump needs to stop pumping.

Thanks to this switch, the water pump only works when needed to!


How do you adjust the pressure switch?

When you get the protective cover off, you'll see the inner workings of the switch. 

Pressure switch for water pump


You will see a large spring and a small spring, both with a nut on top.


These nuts are the ones you need to turn in order to adjust the pressure switch of your water pump.


Adjusting the pressure switch

With the nut on top of the larger spring, you raise the cut-in AND cut-out pressure of the switch by turning it clockwise. If you turn it counter-clockwise, you will lower both pressures.

If you only want to change the cut-out pressure, you adjust the nut on top of the smaller spring.

Again, turning it clockwise will raise the cut-out pressure, turning it counter-clockwise will lower it.

Don't go too high with the cut-out pressure.

You will put a lot of strain on your piping when the pressure is too high. A pipe might even jump!

Adjust it in that way that you have a comfortable stream of water out of your tap.


Troubleshooting your pressure switch


1.The pump doesn't kick in...

A possible problem might be that the contacts are corroded. Open the unit and inspect them.

cleaning the contacts


Get some sandpaper with a grit like 280 or something, and rub it over the contacts.

Clean the contacts and spray some corrosion inhibitor on it.

Check the working of your pump.




Another cause might be that there is dirt in the small connection between the switch and the water pump.

Dismount the pressure switch unit and clean the passage.

Mount it again and use some thread sealant.


Thread sealant


Check all your electrical connections.

See if they are all tight and clean. If not, clean them with some sandpaper, kitchen paper and tighten the connection. Spray some corrosion inhibitor on the connections.

Check the fuse and the switch in the electrical circuit too!




It might also be that your pressure switch unit is just defect.

To check if your water pump itself is working, you could connect the 2 wires that are connected to the switch, with each other, so that you close the electrical circuit. The pump should run now. If not, the water pump might be defect.




2.The pump runs, but doesn't stop anymore.

When your pump kicks in, but refuses to stop, check if all taps onboard are closed. It might be that something is dripping.

You might have a tube that just jumped and caused a leak, so that the pump thinks there's a shortage of water in the circuit.

If you are sure that all taps are closed and there is no leak, then it might be an electrical problem.




What sometimes happens is that, when the voltage of your battery is dropping, that the pump doesn't have enough power to reach the cut-out pressure and thus stays activated.

In this case, charge your batteries or replace them, when you see that they cannot hold their voltage anymore.

You could also make the distance shorter of the electrical wiring from the battery bank to the waterpump. Depending on the size of your boat, there might be quite some distance that the wire needs to go. The longer, the more there will be a voltage drop.


Hope this helps to get everything working again!

Happy showers!



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