Water Pump Running Continuously

[bluelapsing]

Evening all,

 

I've read through a few threads where I think something similar is happening but still unsure what's going on...

 

So the water pump (SHURflo Marine Fresh Water Pump) runs continuously now when switched on. I'm connected to shore power and the noise was initially brief (around 3 seconds) and intermittent. Thought this might be due to the tank being low which initially it was, but since then it's started again except now it's non-stop!

 

I've checked all over and can't see any obvious signs of leaking. The manual mentions air trapped in outlet side or pump head and checking for correct voltage to pump, and also something about pressure switch operation or internal valves being open.

 

Another weird factor is when I ran the engine yesterday I left the pump on and the dodgy meter outside, which is below 12V when I'm starting up the engine, ticked over a bit and when I switched the engine off and came back inside the noise had stopped (until I ran the taps again).

 

Does this electrical/mechanical hogepodge indicate an obvious problem to anybody, ideally with an equally obvious and simple solution? For context, the boat is 20 years old and I don't know when they installed or changed and parts on the pump, but suspect very rarely since the boat was usually left standing on a leisure mooring for most of the year.

 

I'm away from the boat tonight but can provide pictures/further details in the morning

 

TIA

[rusty69]

Sticky pressure switch. Give it a tap

[Tony Brooks]

First of all what is the battery voltage right now? This might just be very flat batteries - not enough power to pump the system up to cut out pressure. We need the voltage of whatever battery feeds the pump, normally the domestic bank.

 

You should not be letting the engine tick over for long, it is not good for it. Run at 1200 to 1500 RPM for at least 4 hours plus, you can reduce that a bit as the batteries charge.

 

I doubt we can say more until we know a bit about the batteries.

 

If you are the poster who asked about heating on a boat new to you, do not use the outside voltmeter, use the inside one set to "domestic". If that is you, then faulty/flat batteries were suggested in the last topic.

 

A well charged battery should read nearly 13V just before start up and no less than 10.8 volts while cranking (Lucas figure).

 

Remember that you probably have two lost of batteries. A single one just for starting and a bank of several all connected together for your domestic electricity.

Edited November 30, 2023 by Tony Brooks

[Momac]

I cured a reluctant to cut out Flojet pump by taking it partly apart , cleaning the insides diaphragm bits  of some very slight limescale and putting it back together . Cleaned the inlet filter gauze at the same time. New O rings on the filter and the inlet/outlet fittings.

The pressure switch may be removed and operated by finger pressure to see it is working .

But that may or may not work for you. Water pumps don't last forever .

[dixi188]

As a slight aside to this thread, I inadvertantly left my Shurflo Trailking 10 pump turned on with the water tank valve closed when I left the boat earlier this year. When I returned about 6 weeks later the pump was still running, and has been fine ever since. So these pumps are OK running dry for long periods.

Dixi.

[ditchcrawler]

Low voltage can definitely cause it to keep running 

[Tony Brooks]

28 minutes ago, ditchcrawler said:

Low voltage can definitely cause it to keep running 

 

Which is why I said we need battery voltage readings,

 

1 hour ago, bluelapsing said:

I left the pump on and the dodgy meter outside, which is below 12V when I'm starting up the engine, ticked over a bit and when I switched the engine off and came back inside the noise had stopped (until I ran the taps again).

 

 A short while on tick over is not long enough to recharge the batteries, but it is long enough to allow the charging voltage to bring the pump up to pressure, at which point it would cut out, whatever the battery voltage, and stay off until a tap let the pressure out.

 

Whilst it MIGHT be a pressure switch problem, the symptoms are consistent with low battery voltage.

 

 

[Jen-in-Wellies]

Does the system have a calorifier? If so, the pressure relief valve could be dripping. The most common type has a red handle. Turn it a quarter turn to open it up and clear any scale that is letting it drip.

[David Mack]

Intermittent running of the water pump with all taps off indicates a water leak somewhere. Continuous running with all taps off means the pressure switch is failing to cut out. Given what else you have described the most likely cause is that the battery voltage is too low, and so the pump doesn't have enough power to pressurise the water to the cut out pressure, hence the pump keeps running (which in turn further flattens the battery). Running the engine raises the battery voltage enough for the pump to cut out, and as long as you don't open any taps and have no water leaks the system will stay pressurised and the pump won't run. But the first time you open a tap after stopping the engine, the pump will run continuously again.

In other words this is a battery/charging problem, and it sounds like your water system is fine.

As a temporary workaround turn the water pump off at its main switch ( you do have one...) when not running any taps.