How can I double shoot this issue? 12v Water Tap..

[devs]

Hi guys, I've got a simple 12v water tap that acts as a switch to a water pump.

Its failed somewhere and I'm unsure if its the tap or the pump that I need to replace? What tests could I perform to trouble shoot this please?

I've attached a couple of photos so you can see what I'm working with.

Blue and earth wires to 12v battery
two white to tap
two white to water pump

Thanks,

Steve.

 

[EFLImpudence]

Do you have a multimeter?

If so, test for 12V where it should be.

 

[devs]

Hi and thanks I don’t unfortunately but will try and get hold of one. Trust I would check that the tap is sending current?

 

[Taylortwocities]

Trust I would check that the tap is sending current?

No, the tap wont send current, Unless you count the current in the flow of water!

Suggest you check that you have 12v from the battery.
Connect the battery direct to the pump, bypassing the tap. If the pump runs then it isn't the pump!

Note that no meter is needed for this!

Then (I'm guessing) you could assume that the tap is faulty, or you could use the continuity setting on your nice new meter (you have to buy one now) and see if there is continuity when you turn the tap on.

 

[devs]

Perfect, thanks very much for the help. It’s appreciated. I’ll get to work

 

[john4703]

That looks like the set up in a caravan. If it is make sure the pump is firmly plugged into the socket on the caravan and that the terminals are clean.

 

[Harry Bloomfield]

If the tap has wires going to it, then it is of the tap with built in switch variety. In which case they usually include a microswitch operated by turning the tap on. If it is that which has failed, the microswitch is a standard part, commonly available and easy to replace. Turning the tap to on, you should here the click as the switch operates.

Another method used is a pressure switch system, where the entire water system remains pressurised. A none-return valve goes in the pipe leading from the pump, a drop in pressure when a tap is turned on, makes the pressure switch turn on, powering the pump to run.

 

[devs]

Hi guys just back and had a look at this it seems to be the tap that has failed at the pump runs when directly connected. Anyone know how to access the microswitch in these or is it a full replacement? Thanks

I’ve had a look and popped both end caps off but can’t see the switch.

 

[Taylortwocities]

Hum, nasty wet thing. Maybe better to ask on the plumber's forum?

 

[Harry Bloomfield]

I’ve had a look and popped both end caps off but can’t see the switch.

If you have confirmed there are actually wires going up into the switch first - have you? Then the switch will be located under the tap control knob. It looks in the photo, as if the plastic part in the middle of the knob comes out, in which case, there will be a screw hidden under it, which retains the knob on the tap.

Other than that, look for a grub screw via a hole in the circumference of the knob.

A work around, would be to add a n/o push button across the two wires leading to the tap - turn the tap on, and press the button - water comes out.

 

[devs]

Thanks yes there’s wires going up top the tap. I’ll disconnect it all and take a good look at it. It’s not the end of the world as I can buy a new one for £20 but if it’s an easy fix I’ll save it from landfill. Thanks for the help

 

[cdbe]

Quite common to use a doorbell when the microswitch burns out (they don't like the current drawn by the pump).

 

[jj4091]

It is a Comet London Tap with micro switch caravan motorhome comet london mixer tap chrome not exactly the same model as yours but this shows how to get into it

 

[ericmark]

You can get pressure switches designed for the job with one way valves so no need to repair the tap.

 

[Harry Bloomfield]

You can get pressure switches designed for the job with one way valves so no need to repair the tap.

There are pros and cons to both system designs. A problem with the pressurised system using a pressure switch is that if you suffer a leak, the entire contents of the water barrel ends up in the vehicle. Another issue is that if you run out of water in the barrel, the pump will run continuously dry, until you notice. Which could be many hours if the pump and barrel is outside. To help avoid those problems, I fitted a piezo oscillator/sounder across the pump terminals - every time the pump runs, it sounds.