Water Pumps

[Suua]

Hello can someone please confirm if this is correct.
The upper pipe is the inlet, the lower the outlet.

Water Pump2.png (496.93 KiB) Viewed 1392 times

[Nereus]

Yes, that's correct. The bigger pipe is always the inlet.

[Suua]

Many thanks, just needed confirmation as I'd heard conflicting reports

[Suua]

Many thanks

[buksida]

Got a strange problem with our Mitsubishi water pump which is very similar to the one in the picture above.

Govt water in our area was cut off for about a week, giving us a trickle in the middle of the night, so we have been running off the underground tank using the pump. In a rare senior moment, mrs Buksi left one of the outside taps on and the pump emptied the tank by running all night. Now it just won't behave at all.

The tank has been refilled and the pump will draw water from it but won't shut off. The pressure switch was the first thing I looked at and replaced it with a new one but the problem remains. The pump is pumping from the tank but it just keeps running, it doesn't quite sound right either as if there is air in the system but I checked that and made sure it was primed.

Any suggestions before we call someone out?

[Nereus]

Those pumps use an "air cushion" to obtain the pressure. If it is not shutting off it idicates that there is not enough space in the tank to form the air cushion. Unplug it from the power, open one of the drain plugs around the bottom of the tank, there are usually 4 of them, one being used to suck from the water supply.
Let all the water drain out, repalace the drain plug and power. You MAY have to re-prime it, although draining the tank it should not lose it's prime.

[buksida]

Thanks for the suggestion, tried that and a fair bit of water came out. Re-tried it and the problem remains, it still wont shut off.

[Nereus]

Most pumps also have what is called a "snifter valve" in my speak. Its function is to bleed off any water that gets up into the sensing connection of the pressure switch. I am not familar with your pump, so cannot tell you where to look, but I will say that as it was working previously, the problem is in the pressure switch area. Any water trapped in that area will prevent the pressure switch from working.

[malcolminthemiddle]

Thanks for the suggestion, tried that and a fair bit of water came out. Re-tried it and the problem remains, it still wont shut off.

Are you sure all taps including garden taps are tightly turned off? These pumps are normally "on demand" type.

[buksida]

Yep, tried all that, its still playing silly buggers so will get someone that knows about them to have a look, its beyond me, I'm no pump expert!

[stretch]

Think you have one leak or more after a time the joints underground give in .

[Nereus]

If the people that installed the pump originally had bothered to fit a shut off valve on the outlet of the pump, then it would be a simple matter of closing the valve to eliminate the rest of the system.

Time and time again I see these pumps without a shut off valve installed, so when there is a problem somewhere on the system, the whole system including the pump, has to be drained down just to fix a simple tap leak.

[buksida]

If there was a leak in the house pipes, the meter would spin when the pump is isolated and our water bill would be horrific, it isn't. We only use the pump and tank in an emergency when the govt water is low or off (which has been most of this month).

We fitted inline taps/valves on the inputs and output of the pump so can completely isolate it from the rest of the system since we don't use it all the time. It still wont shut off even when these valves are closed which leads me to believe it could be electrical but whadda I know?! Need a pump guru to take a look but nobody can be arsed to work around here!

[Nereus]

As you have posted, it has run dry. It is possible that the impeller has been damaged and the pump is no longer producing enough pressure to operate the switch. Short of trying to measure the pressure, you could try adjusting the switch down a bit and see if it then stops.

The pressure switch is the sole controller electrically, it does not have a relay, but switches directly.
You have wired the new switch up correctly havent you?

Is the pressure switch mounted seperately with a plastic tube going too it, or is it mounted directly into part of the housing? In either case, it may be blocked with some crap picked up when it ran out of water.

If you have a source of air pressure, such as a tyre pump, you could try blowing some air though whatever is accessible with the switch removed, and power off. The switch only has a small switching range, usually about 2 bar on, up to 3.5 bar off. Some switche's have a means of adjusting that differential range, but not all.

[buksida]

Yep, the pressure switch is wired correctly, it is brand new so no shit in there or the housing where it is mounted onto. I'll try tweaking the adjustments on it (but it had the same problem with the old pressure switch which probably still works).

Sounds like the thing just needs pulling apart, cleaning out, servicing, and re-setting up (it is a few years old) ... just cant get anyone in the boonies to do it.

Luckily, the govt water has been on for the past week so we don't need the pump ... but there will be a next time ...