Problem with Water Pump

[Flash500]

I have a Mitsubishi WP-105P automatic water pump on my 2-storey house which when I turn on any taps, showers etc it turns on and off constantly therefore the discharge of the water is low/high/low/high etc etc, is there any setting inside to adjust to get a constant even water flow? or is this normal ? (cant see that being the case!)

Any help/advice greatly appreciated.

[KhunBENQ]

If you fully open the taps then there is definitelty "something wrong".

There are set crews usually under some separate housing with which you can change the lower and upper pressure limit for the pump to start/stop (control hysteresis).

Usuallt you will see a sticker saying "don't change"

A 105 Watt pump for a 2 storey house? Seems quite weak to me.

(We have a 255 Watt for a 2 storey house)

Since when do you have it and since when do you observe the problem?

WP-105P

Question: seems like this pump has a small pressure tank at the bottom?

If so, then the problem might be easier to fix (waterlogged pressure tank).

You have to empty/ventilate this pressure tank.

Someone might be able to describe how (I don't have that).

Edited May 13, 2015 by KhunBENQ

[Flash500]

Thanks for that quick reply, only been in a month and thats how its been since then, just doesn't seem right to me!

I'll have a look when I get in for the pressure tank and also the the set screws......cheers

[KhunBENQ]

If it looks like this, it has a pressure tank:

First point to troubleshoot.

Edited May 13, 2015 by KhunBENQ

[Flash500]

Yes thats it

[KhunBENQ]

A short description regarding the pressure tank is here:

http://www.thaivisa.com/forum/topic/698917-water-pump-pressure-accumulator/#entry7336495

Maybe member @Crossy will jump in

Edited May 13, 2015 by KhunBENQ

[Pib]

If it turning off and on rapidly like runs for say 5 seconds, then kicks off for say only around 1 second, then the pump pressure tank (what the motor/manifold assembly sets on top of) is probably waterlogged. The on-off cycle should be approx equal...like 5 seconds on, 5 seconds off.....3 seconds on, 3 seconds off.....etc.

[Forkinhades]

sounds like an airlock, or inlet valve problem.

[wayned]

The pump that you have is an accumulator type pump. The pump builds up pressure in the "accumulator" tank. It turns on when the pressure gets below a certain setting and turns off when it reaches a higher setting ( the switch that I have turns on at 0.9 kg/cm sq. and off at 1.8 kg/cm sq). The pump will turn on and then off as the pressure varies. The only time that you will have constant pressure is when the pump is running constantly since it can not ever reach the cut-off pressure. There are no adjustments on this type of pump to get "constant pressure".

As Pib said if it it turning on/off very quickly it could be "waterlogged". It actually easy to fix, but the tank must be drained. Turn of the valve to the input of the tank (if there is one), remove power, open a tap in the house until the pressure bleeds off (water stops) and close it. Turn off the output valve from the tank(if there is one), remove the drain plug on the tank and completely drain it. Reverse the process.

I had a WP-105 on my house in Bangkok and it worked fine, but the shower on the second floor was only used occasionally and usually when nothing else was on. When it failed I replaced it with a Wp-255.

[KhunBENQ]

It might be complex to calculate what the normal on/off cycle of such a pump is.

Depends on size of tank, power of the pump, amount of water flow.

At the sister in law they have such a type of pump (WP0155Q3), one story house.

I did a little test.

Opening one kitchen tap with moderate flow (like rinsing the dishes, washing hands etc.):

8 sec pump on, 15 sec pump off

Opening a tap in the bathroom, full blown, strong stream: pump does not stop.

This 8 / 15 sec cycle seems healthy also considering that this type pump is fairly low noise.