Faulty water pump?

[ronnietucker]

After filling my under-floor water tank of my Dawncraft 22 (GRP cruiser) I tried the water tap and, after a second, water came out. Hurrah!

The second time I tried it. Nothing. Not a drop.

I traced the wiring back to the water pump which was under the floor and beside where the water tank is (hence, my now knowing where the tank is). Turning the tap on and off gives me about 2v at the pump, but the pump isn't coming on. I've since tried the tap for continuity and it's definitely switching on/off. I've checked the fuse continuity and it's OK, and I'm getting 12V across the terminals marked as water pump (red and brown) at the fuse box.

NOTE: the wires from the tap to the pump were joined using a block which seemed a bit rusty, so that's been replaced. The wires also seemed reversed as it was giving me -12V at the water pump terminals at the fuse box. Are they meant to be reversed for a reason? Swapping them over didn't make it work anyway.

I'm thinking it's the pump that's dud. Probably due to that rusty joining block. What does the Internet think?

[Tony Brooks]

sounds like a tap with a micro switch. My bet would be on the micro switch. Try joining the ntwo wires that probably hang down below the tap. not the ends that run to the tap, the ends of the cable runs.

[ronnietucker]

1 minute ago, Tony Brooks said:

sounds like a tap with a micro switch. My bet would be on the micro switch. Try joining the ntwo wires that probably hang down below the tap. not the ends that run to the tap, the ends of the cable runs.

I've taken the tap off completely and I can hear it click off/on. I've put a multimeter on the wires coming down from the tap and it was showing continuity when the tap was turned.

I can also see a voltage reading at the pump when the tap is turned on/off.

[Tony Brooks]

But 2V is not enough. It should be zero with the tap turned off and 12V + with the tap on and pump running. 2v at the pump suggests faulty/resistive contacts in the micro switch. I suspect the switch area is full of wet corrosion and crud.

[ronnietucker]

10 minutes ago, Tony Brooks said:

But 2V is not enough. It should be zero with the tap turned off and 12V + with the tap on and pump running. 2v at the pump suggests faulty/resistive contacts in the micro switch. I suspect the switch area is full of wet corrosion and crud.

I wasn't sure if the 2V was to trigger the pump, but if it should be 12V then you could certainly be right with the tap.

Are they worth taking apart and cleaning, or to just buy a new one?

[ronnietucker]

I see micro-switch taps on Amazon for about £15, so I might just buy a tap and see how it goes from there.

[Tony Brooks]

3 hours ago, ronnietucker said:

I wasn't sure if the 2V was to trigger the pump, but if it should be 12V then you could certainly be right with the tap.

Are they worth taking apart and cleaning, or to just buy a new one?

No idea, very much a caravan thing nowadays. Boats usually use a pressurised system.

Don't buy anything until you test the circuit. Under the tap there should be two cables hanging down probably with some form of joints to the boat's wiring. Disconnect the boat's wires and join the together. That should put 12V straight to the pump. If the pump works its the switch in the tap. If it does not then you probably have a very poor connection somewhere else in the pump circuit. Possibly a hidden connection where something else Ts off the 12v supply line OR on the negative. make sure all the screws in the negative bus bar that is usally close to the fuses are tight.

 

[ronnietucker]

20 hours ago, Tony Brooks said:

No idea, very much a caravan thing nowadays. Boats usually use a pressurised system.

Don't buy anything until you test the circuit. Under the tap there should be two cables hanging down probably with some form of joints to the boat's wiring. Disconnect the boat's wires and join the together. That should put 12V straight to the pump. If the pump works its the switch in the tap. If it does not then you probably have a very poor connection somewhere else in the pump circuit. Possibly a hidden connection where something else Ts off the 12v supply line OR on the negative. make sure all the screws in the negative bus bar that is usally close to the fuses are tight.

 

4

Thanks for the tip Tony. I'll definitely give it a try. No idea why I didn't think about bypassing the tap by closing the circuit. Duuhhhh!   

I've bought a replacement tap anyway. It does need replacing anyway.

[ronnietucker]

On 14/08/2017 at 17:10, Tony Brooks said:

sounds like a tap with a micro switch. My bet would be on the micro switch. Try joining the ntwo wires that probably hang down below the tap. not the ends that run to the tap, the ends of the cable runs.

Yep. Spot on, good sir. It was indeed the tap that was faulty.

Thanks for the advice!

[Tony Brooks]

When the new tap also fails I think I would fit a push button switch to turn the pump on and off (like a car's horn push or starter button). Long term that is likely to be more reliable. They will often fit in the front of the sink "unit" so its right by a raised knee.

[ronnietucker]

I see pumps (on Amazon) that are more automatic and turn on when required (ie: when the tap is open). Are they any cop?

[WotEver]

30 minutes ago, ronnietucker said:

I see pumps (on Amazon) that are more automatic and turn on when required (ie: when the tap is open). Are they any cop?

90% or higher of leisure boats have such a system. A pump plus pressure switch; turn on a tap, the pressure drops and the pump turns on. 

[Tony Brooks]

The only thing I would be cautious of is that the OP's boat was probably  plumbed with those taps in mind so the pipework might not like being under pressure all the time so may leak or a hose pull itself off a spigot. At present it only pumps against an open tap. My initial thought was to go for a conventional pump, then I remembered some of the GRP boat lashups I have seen so felt a push button switch would be a less problematical and more reliable solution in the long term.

[WotEver]

34 minutes ago, Tony Brooks said:

The only thing I would be cautious of is that the OP's boat was probably  plumbed with those taps in mind so the pipework might not like being under pressure all the time so may leak or a hose pull itself off a spigot. At present it only pumps against an open tap. My initial thought was to go for a conventional pump, then I remembered some of the GRP boat lashups I have seen so felt a push button switch would be a less problematical and more reliable solution in the long term.

A very good point Tony. One that I had completely overlooked. As you say, his system wasn't designed to be under pressure and might have to be completely renewed if changing over to a pressurised system.