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HeatherHP
HeatherHP

Posted: Sun Jan 13, 2013 11:17am

Post Subject: Fresh Water pump troubles

Hi there, Our water pump has been acting up for the last few days. Recently I have been turning on a tap and I can hear that it hasn't kicked in and no water comes out. Previously, I found that if I turned on another set of taps it would kick in and shortly, everything would be working as normal. However, today neither sets of taps seem to be making it kick in. It shouldn't be an electricity problem as we are on shore hook up, charging all the time. I wondered if it could be an air lock? If so what would I do? Still quite new to boats and not particularly technically minded so all help is appreciated. Thanks! Heather

Tony-B
Tony-B

Posted: Sun Jan 13, 2013 11:44am

Post Subject: Fresh Water pump troubles

I assume the main switch and/or fuse supplying the water pump is turned on. I think it is an electrical problem but not a lack of available electricity. It is very unlikely to be an airlock because if it was the motor would run but not pumps and all modern water pumps are of the positive displacement type that would simply push the air out of the tap. It could be an airlock between the tank and pump if the pump was old but even then the motor would run. Without an age for the boat/pump it is difficult to be precise but I think there are two possibilities. If the pump is many years old a part of the electric motor known as brushes may be worn out and not making a good electrical contact. Perhaps the easiest way if testing this is to turn the tap and an then give the cylindrical body of the pump (the motor) a sharp whack with the rubber heel of a shoe. If the motor starts it is an indication that the brushes may be worn. Unfortunately that is not a 100% diagnosis. On the "not cylindrical end" of the pump where the wires go into it there is a little microswitch that is operated by a small diaphragm. When the system is up to pressure the diaphragm opens the switch to turn the pump on. As the pressure falls a spring pushes the diaphragm back so the switch can turn on and work the pump. I think the problem is most likley to be that the switch is not turning on again. The causes are as follows. 1. The switch being faulty, burnt contacts or a broken part. 2. The diaphragm being old and stiff or the small spring being broken. 3. The diaphragm chamber being filled with scale/dirt. 4. There is a small drilling between the pump output side and the diaphragm chamber. These can and do block. There is also the possibility that there is a loose connection somewhere on the pump's supply circuit. If this were my pump I would take the switch and diaphragm chamber of to inspect, clean, and poke out the small drilling to see if that cures it. However for many fitting a new pump would be easier. If you have a voltmeter or a multimeter set to 20 volts DC (assuming 12V boat) connect it to the two wires running to the pump. If it reads 12 volts or more it is unlikely to be a problem on the circuit. Tony Brooks

HeatherHP
HeatherHP

Posted: Sun Jan 13, 2013 7:49pm

Post Subject: Fresh Water pump troubles

Hi Tony, Thanks for your help! We got the pump out and had a look and managed to fix the problem (we hope). Its a Shur Flo Aqua King pump, we think it was a problem with the pressure like you said, but we found that the way to change the pressure was to turn a screw at the non-motor end near to the diaphram, the screw was described as 'shut off adjust screw - does not change flow or operating pressure'. So its a bit strange that the more we tightened the screw the more the water flow increased. Does that sound alright or a bit of a haphazard quick fix?! Thanks again for your help (at least we can have a cup of tea for now!) Best, Heather

Tony-B
Tony-B

Posted: Mon Jan 14, 2013 10:22am

Post Subject: Fresh Water pump troubles

As the flow increased the pressure must have increased, otherwise the flow would have stayed the same. Unless you have a pressure gauge on the circuit I do not know how you can be sure the cut-out pressure has not increased. The screw you turned is the pressure adjusting screw and it acts on the micro-switch I spoke about. This suggest to me that the switch is faulty and your repair is likely only to be temporary but how long it will last I can not say. There is no problem with running at a higher pressure (within reason) as long as it is not so high it lifts the pressure relief valve that I hope you have on your calorifier off its seat. If it did the pump would tend to run all the time so I expect its OK. If you feel you want to experiment and can get the micro-switch out of the pump you may find that Maplin sells a similar part. If you look at the pump you wills e a cable (normally red) going into the pump body near that screw and another one coming out of the body and going into the motor part of the pump. If you were to join these two wires together the pump would run all the time but you would have water but would have to turn the pump on when you wanted water and off again when done. The reason I tell you this is that I suspect the pump will fail again when you are miles from help. Tony Brooks

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