Problem With Mitsubishi Water Pump

[jbrain]

The pump sucks the water out of the underground tanks then pushes it through 2 filters into a clean water tank.

In the case of my suggestion the pump would have to suck the water through the filters and then deposit it in the clean water tank.. The pump has a suction rating of 9 meter and the suction pipe is about 2 meter below the pump.

[canuckamuck]

Without seeing the setup, and assuming the sediment filter can be used by water being drawn through it rather than pushing through or dropping in. Then i guess it should work.

For my sand filter (home made) I think the sand would be drawn through if there was suction, because it is a gravity system and it is designed for seepage not pressure.

[jbrain]

Without seeing the setup, and assuming the sediment filter can be used by water being drawn through it rather than pushing through or dropping in. Then i guess it should work.

For my sand filter (home made) I think the sand would be drawn through if there was suction, because it is a gravity system and it is designed for seepage not pressure.

This is the kind of sediment filter I'm talking about. How one can know if it can be used to suck the water through instead of pushing ?

[canuckamuck]

I suppose a company website might help.

One more thing i hadn't considered is that too much resistance from the intake end could cause cavitation.

Pumps can push water more easily than they can pull it. Do you have a sense of how much pressure is needed to move water through that filter? if there is only slight resistance you should be OK.

While I am here,

Anyone have an answer for post 87?

[jbrain]

I need a little help my WP155q3 Mitsubishi pump.

For the last few days it has, occasionally, continued to run, but not make any pressure in the water line to the house.

When I open the screw top nearest the intake. The one with the spring loaded valve in it. there is pressure there and the water is near boiling.

Also if I open the screw top on the pressure tank itself, there is plenty of pressure there as well.

If I shut the pump down, release the pressure from the top opening, and then run the pump again. generally it returns to normal operation. Sometimes for 10 hours or so before having the problem again.

Any ideas

The water supply is not inconsistent. there is a 2000 liter tank beside it which has not been empty in months. Water goes to the pump with pretty good pressure and a 1 inch line

I had a similar issue not so long ago and it turned out to be a little fit at the suction pipe where it would suck air. First i thought it was the pressure switch, and I purchased a new one but hadn't installed it yet, then I noticed that when I poured water in the pump to prime but kept the pump switched off, the water would slowly disappear.

One connection in the suction pipe wasn't glued.

Pump would make a lot of internal air pressure .

[Pib]

Below is a cut and paste from a web site that I think gives a good summary of how a water pump pressure tank works...how "air" in the tank is compressed to to create an energy spring so to speak. If that air leaks off/is not kept at a certain charge, then that energy spring is loss since water is a liquid and can't be compressed. For the Mitsubitshi type pumps/tanks there is no rubber diaphragm in the tank to keep the water and air separated to prevent the air from being slowly absorbed into the water; therefore an air charger/balance/control valve is used to add just a little air on each pump cycle to keep the air charge correct which creates that energy spring at the correct level.

Also, when draining the water from the tank be sure to let it completely drain out which then allows air to rush into the tank...air that will be compressed to its initial pressure level when you put the drain plug back in and start up the pump. And "if" the water pump's air charger/balance/control valve is working properly that valve will keep the air charge at the correct level; if it ain't working properly (like maybe the rubber diaphram within the valve is ruptured) then it can't add that small charge of replacement air on each pump cycle to replace that little bit of air which is naturally absorbed into the water at the water and air boundary.

Summary: all water in a water pressure tank is bad...a.k.a., a waterlogged tank...can cause the pump to quickly cycle...run most of the time...overheat; the proper balance of water and air in the tank is good....that air spring is doing the pressure work while the pump is off/resting/cooling off.

In a closed, automatic water system a pressure tank is used to store water and maintain system pressure between specified limits (such as 30 to 50 PSI). As the water level in the tank rises, tank air is compressed in the upper part of the tank until the upper pressure limit is reached (i.e., 50 PSI). At this "cut-out" point a pressure switch opens the electrical circuit to the motor and the pump stops. The compressed air in the tank acts like a spring pushing down on the water to create system pressure. When a valve is opened in the water system, the air pressure in the upper part of the tank forces water to flow out of the tank and into the system. As the water is drawn from the tank, the air occupies a larger space and the pressure drops until the lower limit is reached (i.e., 30 PSI), At this cut-in point the pressure switch closes the electrical circuit to the motor and the pump starts. A cycle is thereby completed.

Glad I found this thread.

I have a small automatic centrifugal pump which pumps the water from one tank to another. The pressure switch on that pump reads - on : 1.1 Kg - off : 1.8 Kg.

It had such a I think 0.5 liter pressure tank attached to it, and I have replaced that with a 24 liter pressure tank in the hope it switches on/off less frequently when filling up the water tank.

What pressure do I need to put in the pressure tank ?

Most likely 1.0Kg with the tank empty. Seems the rule of thumb is to set 2psi (approx. 0.1Kg) "below" the cut on pressure....your cut off pressure is 1.1Kg. From what I've seen those small screw-on pressure bottles are usually pre-pressured to approx. 1 bar. See this Link for more info. Good luck.

[jbrain]

Below is a cut and paste from a web site that I think gives a good summary of how a water pump pressure tank works...how "air" in the tank is compressed to to create an energy spring so to speak. If that air leaks off/is not kept at a certain charge, then that energy spring is loss since water is a liquid and can't be compressed. For the Mitsubitshi type pumps/tanks there is no rubber diaphragm in the tank to keep the water and air separated to prevent the air from being slowly absorbed into the water; therefore an air charger/balance/control valve is used to add just a little air on each pump cycle to keep the air charge correct which creates that energy spring at the correct level.

Also, when draining the water from the tank be sure to let it completely drain out which then allows air to rush into the tank...air that will be compressed to its initial pressure level when you put the drain plug back in and start up the pump. And "if" the water pump's air charger/balance/control valve is working properly that valve will keep the air charge at the correct level; if it ain't working properly (like maybe the rubber diaphram within the valve is ruptured) then it can't add that small charge of replacement air on each pump cycle to replace that little bit of air which is naturally absorbed into the water at the water and air boundary.

Summary: all water in a water pressure tank is bad...a.k.a., a waterlogged tank...can cause the pump to quickly cycle...run most of the time...overheat; the proper balance of water and air in the tank is good....that air spring is doing the pressure work while the pump is off/resting/cooling off.

In a closed, automatic water system a pressure tank is used to store water and maintain system pressure between specified limits (such as 30 to 50 PSI). As the water level in the tank rises, tank air is compressed in the upper part of the tank until the upper pressure limit is reached (i.e., 50 PSI). At this "cut-out" point a pressure switch opens the electrical circuit to the motor and the pump stops. The compressed air in the tank acts like a spring pushing down on the water to create system pressure. When a valve is opened in the water system, the air pressure in the upper part of the tank forces water to flow out of the tank and into the system. As the water is drawn from the tank, the air occupies a larger space and the pressure drops until the lower limit is reached (i.e., 30 PSI), At this cut-in point the pressure switch closes the electrical circuit to the motor and the pump starts. A cycle is thereby completed.

Glad I found this thread.

I have a small automatic centrifugal pump which pumps the water from one tank to another. The pressure switch on that pump reads - on : 1.1 Kg - off : 1.8 Kg.

It had such a I think 0.5 liter pressure tank attached to it, and I have replaced that with a 24 liter pressure tank in the hope it switches on/off less frequently when filling up the water tank.

What pressure do I need to put in the pressure tank ?

Most likely 1.0Kg with the tank empty. Seems the rule of thumb is to set 2psi (approx. 0.1Kg) "below" the cut on pressure....your cut off pressure is 1.1Kg. From what I've seen those small screw-on pressure bottles are usually pre-pressured to approx. 1 bar. See this Link for more info. Good luck.

Thanks for the response. Since you seem to be knowledgeable about water systems, do you also know if it is possible to have the pump installed after a Big Blue filter as shown in my previous post with a sediment cartridge inside ?

[Pib]

Thanks for the response. Since you seem to be knowledgeable about water systems, do you also know if it is possible to have the pump installed after a Big Blue filter as shown in my previous post with a sediment cartridge inside ?

I really couldn't say, but my gut is telling me the water could not be provided through the filters fast enough to satisfy the pump and pump damage/constant running/overheating could occur...stuff like described at this Link might happen. It would be like trying to suck a thick milkshake through a really small straw....makes you feel like your head is going collapse inward because you are sucking so hard but not getting no shake to the inside of the mouth.

[Crossy]

Our crunchy-bits filter is on the inlet to the water tank, so tank water is clean before it goes near the pump.

[jbrain]

Our crunchy-bits filter is on the inlet to the water tank, so tank water is clean before it goes near the pump.

But I assume that you have the mains pushing the water through the filter into the tank.

[Pib]

Our crunchy-bits filter is on the inlet to the water tank, so tank water is clean before it goes near the pump.

But I assume that you have the mains pushing the water through the filter into the tank.

Plus a crunchy-bits type filter (maybe a mesh type strainer) offers little resistance to water flow....probably around a 100 mesh/150micron filter used to stop larger dirt/gunk particles...not like the filters you are talking about which are probably filtering down around the 5 micron size....or said another way a milkshake straw 30 times smaller in diameter (i.e., 5 microns compared to 150 microns).

[Crossy]

The filter in question is one of the cotton jobbies, no idea what size it is but it keeps the occasional mud coloured water out of our tank.

Mains pressure can be awful but recovers enough at night to top up the tanks.

[Goat Roper]

Without seeing the setup, and assuming the sediment filter can be used by water being drawn through it rather than pushing through or dropping in. Then i guess it should work.

For my sand filter (home made) I think the sand would be drawn through if there was suction, because it is a gravity system and it is designed for seepage not pressure.

This is the kind of sediment filter I'm talking about. How one can know if it can be used to suck the water through instead of pushing ?

In my experience you should never filter on the suction side of the pump, always filter on the output/pressure side. A foot strainer on the suction side is what you should have, not a filter. IMO.

[CharlieH]

Please do not cross post the same issues in different topics/threads.

[Murray Greenfield]

Like a lot of people i have been trying to solve a problem with a Mitsubishi Constant Pressure Water Pump in the 2 story house I have been renting for 3 years, First tenant following the owner doing a complete gutting and re build (so was like a new house) so the pump was about 2 1/2 yrs old when the capacitor (250 baht) went up in smoke. New capacitor fitted and all good for 6 mths then this time the capacitor melted, Just leading up to that the pump would cycle as if a tap had been dripping and the in the shower the water pressure would pulse instead of constant pressure, Then the pump would stop (turn off) or sometimes keep running but no water coming out. Turn power off, leave for a while and work again, so my next step was the pressure switch, was about to buy a new switch when I found a closed forum on Thai Visa from 2009, with many pages of comments and advice for exactly my problem. much help and advice until someone finally mentioned the Flapper Valve fitted to the inground tank pickup pipe. Forget the Capacitor or the Pressure cutout Switch beeing the problem, the pump was fine, but the Flapper Valve was not sealing any longer and water was leaking back into the tank allowing air into the pump causing it to overheat and cutting out. The following images are of my Flapper Valve after only 3 years use. Problem Solved.