water submersible pump

[Sparky78]

Hi all, me and my wife are new to caravaning, and recently brought a swift challenger. I am asking advice about the water pump, do you leave it running at all times in the water tank or do you turn the pump on only when water is required. If i leave the pump running all the time you can hear it pumping when water is not required. Is the normal?
Many thanks
John and Donna

 

[colin-yorkshire1]

no its not normal could be a badly adjusted pressure switch the pump is left switched on but should turn it's self off when the system is repressurised after turning off the tap.

 

[ProfJohnL]

Hello John and Donna,

Colin's reply is most likely correct but it's a bit thin on detail.

There are basically two types of water systems used in caravans, those that use a pressure switch, or the alternative uses micro switches in each tap.

As far as I know Swift Challengers have used pressure switched systems.

The pressure switch is usually mounted in a bedding locker close to where the pump connects to the caravan. It usually has a knurled adjustment knob that can be turned by hand.

It also incorporates a none return valve which is essential to the operation of a pressurised system.

The system works on the basis that when no taps are open, the pump is capable of raising the pressure in the pipework. The pressure switch detects the rise in pressure and turns of the power to the pump. Because the taps are off the system is dead ended, and because of the none return valve the raised pressure is locked in the pipework. This keeps the pressure switch in the off position.

As soon as you open a tap, the pipe work is unlocked and as the water escapes the pressure drops, The switch detects the drop and turns on the pump.

Whale were the major suppliers of these devices and they have adjustment instructions available on line at:

http://www.whalepumps.com/documents/pressure_inst.pdf
In addition Please note:
Due to the resilience of the plastic pipework, and the air cap in the hot water heater, the pump may continue to run for a few seconds after the taps have closed as the pressure stretches the pipework slightly and re-pressurises the hot storage tank.

Sometimes, especially if the hot water heater has been turned off after use, as it cools and the water and air contracts a little the pressure in tank diminishes this may happen over a few hours. The pressure switch may detect this and blip the pump for a second or so. This is normal but it should not happen more than a couple of times whilst it cools.
If the pump is continually turning on and off when water is not being used, then it points to leak somewhere in the system. It could be a dripping tap, or it might be a leaking joint on the pipework, But it might also be a leaking None return valve in the pressure switch which you can't see as it drains back to the water container. Sometimes thes can be cleaned, other wise they need replacing

I hope this is useful for you

 

[RegandPat]

I have the same problem, it blips every 5 seconds, drives you nuts at night so I have been switching it off at bed time.
Now reading this post and armed with knowledge I fixed up the outside pump with a can of water switched on power, wiped out the seating at the front and found hopefully the adjuster, now the bad bit.
Well not to bad, it blipped every 5 seconds so turned screw ante clockwise 6 to 8 turns and now it blips every 18 seconds.
I can live with that. (just).
I did change the little 'O' rings out side van but that did not do any good.
Would consider changing the unit that you plug the pump into if not to expensive and hopefully an easy job.
Reg and Pat

 

[ProfJohnL]

Hello Reg and Pat

Your symptoms are classic slow leak somewhere. If you can find a dripping tap or a damp union on the system that i likley to be the problem, or it might be a leak on the water heater, But what you cant easily check is if the none return valve on the pressure switch is not sealing properly as it will only leak bak into the water barrel.

 

[RegandPat]

Thats it then, I will get Pat to crawl under to see if she can spot a leak, just got to break the news to her.
I did look at what joints I could see and listened for any dripping, will have a look again this week end.
Thanks for the pdf file, I am collecting snippets of information as I go and saving them some place unbeknown to me on my hard drive.
Reg

 

[colin-yorkshire1]

Hello John and Donna,

Colin's reply is most likely correct but it's a bit thin on detail.

hi john,
I did in fact write a full explanation covering just about all the points you rasied exept the link which I did not have, unfortunatly while I was previewing the post, "macafee" decided to reboot the computer after a update so it was lost ,
as the time was quite late I quickly posted what I thought was the likely cause with the intention of re doing it later but seeing as how you have done a exelent job of explaining it there was no need.
there is only two points I could add the instrutions on the pressure switch clearly state that the switch should be adjusted regulary and explains how to do it and one for Reg, if after the switch is adjusted properly and it still keeps intermittently cutting in with no leaks on the system the most likely cause is the non return valve BUT stand alone ones can be bought from car accessory shops that fit into the fuel line and are the right bore for the water pipe cost about a fiver but cheaper than the original unit and do exactly the same job,
colin

 

[ProfJohnL]

Just an additional note about submersible pumps.

Most submersible pumps need to have water running through them when they run, They rely on the water to help cool the motor. If for any reason the water flow is blocked or there is no water in the container and the pump is running for more than thirty seconds, the pump will start to warm up. If left for too long the heat from the motor will damage shaft seals and in the worst cases will start to melt or deform the pump housing.
Even if the housing has not deformed, the hot motor will heat up the air inside the motor houseing which will raise its pressure. If the sahft seal is worn that prerrurised air may blow past the shaft seal. Equally when the motor cools, the housing pressure will drop and tha might suck water past the shaft seal into the motor housing. Water and motors do not mix, so before long the pump will start to fail.
Both types of pump control (pressure switch or Microswitches) can cause this type of problem, so its worth getting pump control problems sorted out.

Replace any faulty microswitches as soon as possible or as an emergency cut the wires under the tap for any faulty switches.
Ensure your pressure switch is correctly adjusted

Always turn off your pump when you leave the caravan, (just incase some lo-life pinches your water container) and it is good practice to turn it of over night.