Water Pump Issue WP-255-QS

[rickirs]

Purchased a new 3-bedroom 2-bath townhouse in a new subdivision in Bang Khun Thian, Bangkok suburbs.

Had a Misubishi electric water pump WP-255-QS (distributed by Kang Yong Electric PCL) installed with holding tank.

For personal reasons I have not moved into place after several months nor have installed any electric appliances. But during that time I would go to water the new lawn and plants. Then start getting Bt1,500/mo electric bills. I noticed that pump is always very warm and it never seemes to shutoff. I shut it down and subsequently turn it on only to water lawn, Then electric bills went down substantially to about Bt75/mo. (usage + fixed cost). Water bills are nominal-seem right for just watering lawn.

I think the problem might be the pressure switch? I have read in the forums that sometimes pressure spring or electric switch will stick; or switch might need replacement. Those are things I can do but the schematics for the pump are in Thai only. I went onliine to both Misubishi and Kang but do not find any in english. I tried to contact by email and get no responses.

How can I get schematics in english?

What seems to be the problem?

[gerry123]

take photos of offending parts and manufactures /serial number plate /sticker go along to any decent pump shop and bobs your uncle

easy to fit such parts or better still remove parts and match at shop

[bankruatsteve]

Also check the plumbing. For example, if there is connection after the pump to the mains, make sure there is non-return valve or that the valve is closed when the pump is in operation. Make sure all faucets are off and no leaks.

[splitlid]

install a simple valve after the pump and close it off, if the pump stops then there is a leak somewhere from that valve to the household appliances.

if the pump keeps running, then there is a pump problem, have you bled it? have you unscrewed both caps and filled them with water and tried again?

[wayned]

I think that if you look closer at the label it will be a WP-255Q3. It's and acccumulator pump with the tank on the bottom. The Mitsubishi pumps do not have bladders. The first thing that I would do is turn the pump off and turn off the water supply into it. Then find the drain valve on the side of the tank and drain it completely, open a faucet first to relieve the pressure. After it has drained completely replace the drain pug, turn on the water supply and the electric. It should run continuously until the pump shuts off. These pumps become "waterlogged" especially after sitting over long periods with no usage. Since they are not bladder pumps all of the air in the tank is absorbed by the water.

There is not much electrically to fix. The pressure switch is basically a replacement part, about 700 baht. The only other electrical parts are the motor and the start capacitor which is in the small plastic box on top of the motor. I'm not sure how your electric bill got up to 1500 baht as the 255 is a 250W pump and if it ran 24 hours a day for 30 days it would consume 180KWH. Where I live 1 KWH cost 4.60 baht so that would only cost 828 baht!

[bankruatsteve]

From a while back, I think it was determined that the watt rating for a pump does not seem to relate to the energy consumption but rather the head. Example: my 280W Hitachi uses about 4 amps while running.

[wayned]

Interesting!

I assumed that the label was motor power consumption at full load so I just measured my 255Q3. It draws 2.32 amps when running so the simple power consumption is 510W. Even at that it would have to run 21 hours/day to cost 1500 baht here.

IMHO I think that the place to start is drain the pump to eliminate the possible/probable "water log" and go fro there as far as checking for leaks or pressure switch problems.. It will be easy to determine if there are any leaks but might be hard to find them.

[kamalabob2]

There might be a high volume retailer of Mitsubishi Water Pumps in your area. That same dealer could elect to fix your water pump under the terms from Mitsubishi. The high volume water pump shop to install or repair your Mitsubishi Water Pump would have a repair team such as the Builders Merchants in Birirram. Training teams arrive to teach local Buriram repair people new technology and procedures to explain to the Thai Citizen. The same shop would fix your MP-255- QS in a short period of time.

[rickirs]

Thanks for the suggestions.

[kamalabob2]

I spoke last week with Mr. Artiut Manubrud the Deputy Department Manager Fan & Water Pump in Thailand. He travels with a translator but got his hands dirty showing some of the repair technicians how to solve a Mitsubishi water pump repair problem in Buriram. He told me that if I had any questions about any Mitsubishi water pumps that could not be solved at the official Mitsubishi repair facility in Buriram, to contact him and he would have his technical team respond. He seemed to have a real knowledge of water pump repair procedures according to the woman who speaks English at the Buriram Builders Merchants that installs and repairs water pumps for my house and my wife's village garden. If the OP can not get his Mitsubishi water pump repaired in his province he may think about contacting the after the sales service team of Kang Yong Electric Public Company Limited in Samutprakam.

[wayned]

I do all of the pump repairs myself. I agree that Kang Yong are very professional and up to speed. I buy replacement parts form the office in Bangkok and have the sent EMS. They send me a IPL (illustrated parts list) of the pump so that I order the correct parts and I pay via transfer via my internet account. Order day1, ship day 2, arrive in the morning day 3. I'm about to repair my 255Q3, cracked top pump housing and pin hole leak in the tank (temporarily plugged with a screw washer and rubber washer). The pump's about 7-8 years old.

[billd766]

I have a Mitsubishi WP315 which is basically the same pump.

When I forget to change over my storage tanks and the water runs out the pump will keep running trying to pump something that is not there and can run very hot.

The way I clear that problem is

1 turn off the pump to let it cool down

2 shut off the output valve to the filter and the house

3 open a bleed valve I put in before the pump and then change over my storage tanks

4 when I get a free flow at the bleed valve I shut that off

5 I go back to the pump and disconnect the thin plastic pipe from the pressure valave to the water inlet. This releases the pressure in the pump tank. BE VERY CAREFUL as the pipe is often very hot and will blow pressurised hot water. I always disconnect the bottom black pressure valve connection using a towel and I aways point the pipe away from myself.

6 reconnect the pipe but dont turn the pump on yet

7 loosen the smaller cap of the two on top of the pump and let the water flow into the holding tank then make sure it is tightened properly

8 if every thing is OK turn the pump on with the output valve still shut until the pumps stops as the pressure tank is full.

9 open the output valve after the pump and the pump may run for a short while to pressurise the system

10 when the pump stops again turn on a tap to run some water and turn the tap off the pump should stop shortly afterwards and the system will be OK

11 If this does not work then get a large hammer and "engineer" it. You will probably need a new pump but you will feel better about the rage against the machine.

[Prapaexpert]

^{Propably this is problem with the back valve in your tank.}

^{If the water go back to the tank because the back valve not work prperlya and lose pressure. then the pump have to start all over again everytime to build up pressure.}

^{You can call us at 02-1054545 and we can help you to change back valve (Thai speak checkwow).}

^Janne

^PrapaExpert

[Stuart21]

Try tapping the top of the switch with a screwdriver handle. Often it is a stuck switch - can be freed with a 'tap'. But then may or may not happen again. If it happens again, remove it & replace it.

Switch is vertical cylinder abt 40 mm dia, and about 60 mm tall, with a couple of wires coming out. Usually grey.

Also could be insects (ants) nesting in the switch - take the top off the switch & have a gander.

(Power off first!) Spray some insect repellent in after cleaning it out -

I am looking for recommendations - Hitachi, Mitsubishi or Fujika? (I need the low profile type, with the ~ 2L storage on the right)

??

[Pib]

If the pump pretty much constantly runs when using water versus have an approx 50-50 on/off cycle (e.g., approx 4 seconds on, 4 seconds off) then the pump's pressure tank is water logged...that is, the air in the pressure tank the pump motor/manifold assembly sets on top of is pretty much filled with only water which means it will run almost all the time when using water. When the pressure tank has a proper water and air mixture approx two thirds of the tank will be water (the bottom portion) and the top one third will be compressed air. The air gets compressed by the pumping action and acts like a stored energy spring.

And once properly charged the replenishment air is feed into the tank via the six sided shaped air balance valve that screws into the top of the pressure tank and has a small PVC hose running from the valve top to the manifold assembly water inlet. "If" that air balance valve is defective it will not be able to maintain the proper water & air balance in the pressure tank....after a few days to a few weeks the air in the tank will be naturally absorbed into the water. Each time the pump cycles on and off the air balance valve injects a very small amount of air to offset the amount naturally absorbed by the air & water direct contact within the pressure tank. This pump design does not use a bladder/diaphragm to separate the water and air...that's why it has the air balance valve.

And with a water logged tank even when you are not using water even a very small leak (like a leaky tap, a leaky commode bowl valve, etc) somewhere will cause the pump to turn on a lot because the pump's pressure tank has no compressed air in it to act as an energy spring to push out water...so the pump motor has to turn on.

Now if the air balance valve is good (which is should be since it's a new pump) then the pump's pressure tank is just waterlogged. Kill power to the pump, turn off the input and outlet water valves (hopefully the installer included some), and then unscrew the plug at the bottom of the pressure tank..and let the water completely drain out.. Until the water completely drains out air can not enter that drain hole which then serves as the air to be initially compressed when you turn the pump back on. Screw the drain plug back in, turn on the water inlet and outlet valves and then reapply power to the pump. It's self priming...after about 15 seconds of running it should turn off...you should now have "un-waterlogged your pressure tank" and hopefully the pump will operate normally. If not, you have something else causing the air to leak out, the tank to become immediately waterlogged like maybe the backflow valve on the input of the manifold inlet (it's under that first screw cap...a value with spring on top of it) has been removed/is dirty/etc....you are just losing prime somehow which can allow the air in the pressure tank to escape.

I have a WP255 (250 watts) also...been using it for about 8 years...works fine for my two story house.

[cumgranosalum]

I have a 300WP but it is rapidly switching on and off when i turn a tap on......what is likely to cause this?

[RichCor]

Cumgranosalum, try reading Pib's post just before yours. It seems to describe your issue to a tee. Just need to interpret it for your EXACT Mitsu model.

[wayned]

One caution about Pib's explanation. Turn the input valve off first and then open a tap in the house to relieve the pressure in the tank and then turn off the output vale. Then remove the drain plug. If you don't relive the pressure when you remove the drain plug the drain hole will be the "pressure relief" and act like a fire hydrant until the pressure is relieved wetting everything in it's path. Been there, done that!

[Pib]

One caution about Pib's explanation. Turn the input valve off first and then open a tap in the house to relieve the pressure in the tank and then turn off the output vale. Then remove the drain plug. If you don't relive the pressure when you remove the drain plug the drain hole will be the "pressure relief" and act like a fire hydrant until the pressure is relieved wetting everything in it's path. Been there, done that!

Yeap, good point I left out. The pressure in the tank can make the drain plug go flying out of your hand as you unscrew it from the tank and create a nice stream of pressurized water from the drain plug for a few seconds.

However, but, I still turn off the outlet value just to keep water from draining out of the house/second story back through the pump drain hole. After creating the fire hydrant effect and the plug getting blown out of my hand the first time I did it, I've since got the feel in how to "slowly" unscrew the drain plug for its "last few turns" which relieves the pressure built-up and avoids the fire hydrant effect and water draining out of the house when the plug is completely removed....only the water from the pump's pressure tank drains out. I live dangerously.

[captainWPP]

Good day gents

I recently have been having water pump problems and hope that maybe someone on here can lend me some sound advice.

I have a Mitsubishi WP-205QS pump which we installed on a well a couple years back. The well is hand dug, 6.50 meters deep. There is 2.60 meters of water in the bottom of the well. The foot valve on the suction pipe is mounted approx 50 cm off the bottom of the well, so there is 2 meters of water over the foot valve. The pump supplies our single story house which is about 30 meters from the pump and well.

Over the past few months (while I was working abroad) the pump developed a problem that it would cut out in the evenings as the family was showering, cooking dinner, etc. The wifes solution to this was to wait for 10 minutes or so and then the pump would run again. Once I got home the foot valve broke (the plastic non-return valve inside the bronze housing), so I have replaced that. I notice now that I can plug it in during the morning time and it will run normally all day until around 7 o'clock in the evening, when the family is using a lot of water. At that point the pressure in the water pipes will drop to zero. I have a pressure gauge mounted on the water pipe immediately after the discharge side of the pump and it is registering no pressure. When I go check the pump it is running with the pump very very hot. When I pull the plug to stop the pump and open the 2 screw caps on top of the pump, both the suction and supply sides of the pump manifold are full of (very hot) water. I have checked the foot valve again and it appears to be operating normally. The check valve on the suction side of the pump housing is moving freely.

I changed out the pressure switch last week but that did not change anything. Maybe just as well that I did though because the conatcts in the old switch are quite burnt.

After reading the previous posts I thought that my problem might be a waterlogged pressure tank. I depressurized the pump, removed the 2 screw caps on top of the pump housing and then removed the drain plug on the tank. Let it empty out completely, then put the plugs/caps back on and started it up. It ran fine until around 7 pm, at which point the pressure dropped off, the motor is running and the pump is very very hot. This has been going on for a week or so at this point. I pull the plug on the pump once it develops problems in the evening and then drain the pressure tank in the morning, plug it in and it works normally until approx 7 pm.

I contacted Kong Yang and they replied very promptly. They put me in contact with the Chiang Rai Mitsubishi service center. Since I do not live in the city they arranged for a local service rep here in Wiang Pa Pao to come over to the house today to take a look. Two young lads showd up, opened up the pump housing, looked inside and after listening to my description of the problem said they had no idea how to fix it. They called a senior tech, who stated that the electrical supply in Chiang Rai province dips below 220 volt in the evening when everyone gets home and switches on all their appliances. And that some people have pump problems because of this phenomenon. I was a little dubious but decided to check it out myself. This early afternoon I was showing approx 221 - 224 volts at my electrical outlets. The pump developed the same problem right on schedule at 7 pm, so I rechecked the power supply and found approx 197 volts. The pump runs up to 25 psi but not up to the cut-off point of 28 psi. So the motor just keeps on running and the pump gets very very hot.

Just thinking that the voltage drop in the power supply is approx 10%, and the drop in the max psi of the pump is also approx 10% at the same time. Coincidence? I don't know if a lower voltage would cause a pump to not be able to attain the same max psi, but am hoping maybe someone out there can educate me on this topic.

One more thing - tonight after the pump developed problems I drained the pressure tank to see if that would help matters but it did not change a thing. By the time I got the tank drained and the plugs back in place the pump was no longer hot. I plugged it in and it ran up to a max of 25 psi. So the pressure switch never cut out and the pump never stopped until I pulled the plug.

It's getting pretty frustrating at this point and I would welcome any and all advice on what to do at this point. I have asked Kang Yong for a quote on a new air charger assembly, but maybe that would be a waste of money and wouldn't solve the problem anyway?

I have considered just chucking thi spump in the trash, even though it's only 2 years old, and getting a new pump. But if the problem is the electrical supply maybe I would have the same problem?

Thank in advance tor any advice you can offer.

[Pib]

I contacted Kong Yang and they replied very promptly. They put me in contact with the Chiang Rai Mitsubishi service center. Since I do not live in the city they arranged for a local service rep here in Wiang Pa Pao to come over to the house today to take a look. Two young lads showd up, opened up the pump housing, looked inside and after listening to my description of the problem said they had no idea how to fix it. They called a senior tech, who stated that the electrical supply in Chiang Rai province dips below 220 volt in the evening when everyone gets home and switches on all their appliances. And that some people have pump problems because of this phenomenon. I was a little dubious but decided to check it out myself. This early afternoon I was showing approx 221 - 224 volts at my electrical outlets. The pump developed the same problem right on schedule at 7 pm, so I rechecked the power supply and found approx 197 volts. The pump runs up to 25 psi but not up to the cut-off point of 28 psi. So the motor just keeps on running and the pump gets very very hot.

Just thinking that the voltage drop in the power supply is approx 10%, and the drop in the max psi of the pump is also approx 10% at the same time. Coincidence? I don't know if a lower voltage would cause a pump to not be able to attain the same max psi, but am hoping maybe someone out there can educate me on this topic.

One more thing - tonight after the pump developed problems I drained the pressure tank to see if that would help matters but it did not change a thing. By the time I got the tank drained and the plugs back in place the pump was no longer hot. I plugged it in and it ran up to a max of 25 psi. So the pressure switch never cut out and the pump never stopped until I pulled the plug.

Yes, too low of a voltage can cause your problem. I have a Mitsubishi WP255 which uses the same 2.8 bar/40psi upper pressure level as your WP205. There have been times where we have a brown-out here in western Bangkok where the voltage drops to 180V or below. I have a voltage meter mounted on my power box containing all the circuit breakers so it quick and easy for me to monitor the incoming line voltage.

If the the voltage is down around 180V and a water tap is turned, the pump will kick-on and may not be able to built-up the required pressure (2.8bar/40psi) which allows the pump's electrical pressure switch to cut the pump off. When the pump can't reach that pressure because the pump motor is not spinning fast enough it will continue to run and overheat. When the pump overheats the pump motor's built-in thermal protection device (this device is built into the motor electrical winding) shuts the motor off for usually around 15 to 30 minutes...during that time the motor cools off enough for the motor's thermal protection device to automatically reset itself and the motor starts to run again.

Once again, if the voltage is still too low to make it spin fast enough to reach 2.8bars/40psi which would turn the pump off the pump will run & run until it overheats again. When it overheats again the thermal protection device trips again. As mentioned your WP205 has the same upper pressure cutoff point of 2.8bar/40psi. Its lower pressure set point is 1.8bar/26psi where it cuts on (or any lower pressure). Since your pressure is only reaching 25psi it's at/below the pump turn-on pressure so it turns on....and it can't reach the turn off pressure of 2.8bar/40psi due to low voltage.

Now, I do not know what voltage between 180V and the normal 220V where the pump may start acting like described above...it may start at 190V...200V...I couldn't say what the magic voltage level is. I just know there have been several times where my voltage meter was reading 180V during a brownout, turn a water tap on, the pump starts running, and just won't turn off because it can't spin fast enough to reach the required cutoff pressure. My pump is fed by an above ground water storage tank.

[captainWPP]

Thanks Pib

I was afraid it might turn out to be something like that. Interesting though, that we've lived in this place for 20 years and never had any problems like this until just recently. I was kind of hoping that I might just be able to buy a new pump and get around the problem but I may just run into the same problems with another pump.

Thanks again

[sandmike]

A quick question to the assembled crowd of experts ....

I have a mitsubishi pump with a pressure tank that has been run dry and the shaft seal between the pump and motor has failed and pisses water out. (bought from bigC, uncertain of model no., but wp300 seems to ring a bell, I am not in Thailand right now). Is this seal user repairable ??

Thanks for any help, cheers

Sent by carrier pigeon

[wayned]

I contacted Kong Yang and they replied very promptly. They put me in contact with the Chiang Rai Mitsubishi service center. Since I do not live in the city they arranged for a local service rep here in Wiang Pa Pao to come over to the house today to take a look. Two young lads showd up, opened up the pump housing, looked inside and after listening to my description of the problem said they had no idea how to fix it. They called a senior tech, who stated that the electrical supply in Chiang Rai province dips below 220 volt in the evening when everyone gets home and switches on all their appliances. And that some people have pump problems because of this phenomenon. I was a little dubious but decided to check it out myself. This early afternoon I was showing approx 221 - 224 volts at my electrical outlets. The pump developed the same problem right on schedule at 7 pm, so I rechecked the power supply and found approx 197 volts. The pump runs up to 25 psi but not up to the cut-off point of 28 psi. So the motor just keeps on running and the pump gets very very hot.

Just thinking that the voltage drop in the power supply is approx 10%, and the drop in the max psi of the pump is also approx 10% at the same time. Coincidence? I don't know if a lower voltage would cause a pump to not be able to attain the same max psi, but am hoping maybe someone out there can educate me on this topic.

One more thing - tonight after the pump developed problems I drained the pressure tank to see if that would help matters but it did not change a thing. By the time I got the tank drained and the plugs back in place the pump was no longer hot. I plugged it in and it ran up to a max of 25 psi. So the pressure switch never cut out and the pump never stopped until I pulled the plug.

Yes, too low of a voltage can cause your problem. I have a Mitsubishi WP255 which uses the same 2.8 bar/40psi upper pressure level as your WP205. There have been times where we have a brown-out here in western Bangkok where the voltage drops to 180V or below. I have a voltage meter mounted on my power box containing all the circuit breakers so it quick and easy for me to monitor the incoming line voltage.

If the the voltage is down around 180V and a water tap is turned, the pump will kick-on and may not be able to built-up the required pressure (2.8bar/40psi) which allows the pump's electrical pressure switch to cut the pump off. When the pump can't reach that pressure because the pump motor is not spinning fast enough it will continue to run and overheat. When the pump overheats the pump motor's built-in thermal protection device (this device is built into the motor electrical winding) shuts the motor off for usually around 15 to 30 minutes...during that time the motor cools off enough for the motor's thermal protection device to automatically reset itself and the motor starts to run again.

Once again, if the voltage is still too low to make it spin fast enough to reach 2.8bars/40psi which would turn the pump off the pump will run & run until it overheats again. When it overheats again the thermal protection device trips again. As mentioned your WP205 has the same upper pressure cutoff point of 2.8bar/40psi. Its lower pressure set point is 1.8bar/26psi where it cuts on (or any lower pressure). Since your pressure is only reaching 25psi it's at/below the pump turn-on pressure so it turns on....and it can't reach the turn off pressure of 2.8bar/40psi due to low voltage.

Now, I do not know what voltage between 180V and the normal 220V where the pump may start acting like described above...it may start at 190V...200V...I couldn't say what the magic voltage level is. I just know there have been several times where my voltage meter was reading 180V during a brownout, turn a water tap on, the pump starts running, and just won't turn off because it can't spin fast enough to reach the required cutoff pressure. My pump is fed by an above ground water storage tank.

I also have a WP255 with exactly the same problem. I installed a switch on the outlet that it is plugged into and turn it off when power goes off or there is low voltage and use water supplied by the village supply - a dribble - as I also have an above ground tank. If the pump is old the impeller could be worn and will just not move as much water when it runs slower. I have an old WP155 that still pumps water, but the impeller is worn out and it will never turn off as it will never reach cut off pressure. A new pump might correct your problem now, but when the impeller gets worn you will be back to the same

A new AC assembly from Kong Yang is about 650 baht but it won't fix your problem. I know the price because I bought one recently because I screwed up. I installed a new tank (2500 baht) because I had a leak in the old one at a weld joint and when I removed and installed the AC assembly on the new tank I forgot to remove the small plastic pipe that goes into the hole for the AC assembly before you install the assembly. The result was that it got waterlogged everyday and I have already trashed the old tank. Live and learn.

[Pib]

A quick question to the assembled crowd of experts ....

I have a mitsubishi pump with a pressure tank that has been run dry and the shaft seal between the pump and motor has failed and pisses water out. (bought from bigC, uncertain of model no., but wp300 seems to ring a bell, I am not in Thailand right now). Is this seal user repairable ??

Thanks for any help, cheers

Sent by carrier pigeon

I don't know about user repairable but Thais can repair/rebuild most any pump in the universe when the problem is something basic like that. Best thing to do is try to find a place that sells pump parts (usually most any small-medium vendor that specializes in pumps). I expect it can easily and cheaply be repaired.

[Artisi]

A quick question to the assembled crowd of experts ....

I have a mitsubishi pump with a pressure tank that has been run dry and the shaft seal between the pump and motor has failed and pisses water out. (bought from bigC, uncertain of model no., but wp300 seems to ring a bell, I am not in Thailand right now). Is this seal user repairable ??

Thanks for any help, cheers

Sent by carrier pigeon

Quick answer without knowing the overall condition of the shaft and case --- yes repairable.

[wayned]

Yes they are repairable, I buy my parts from these people in Bangkok and have then sent to me via EMS: https://www.mitsubishi-kyw.co.th/index_en.php?lang=en. If you're anywhere near Buriram there's also an authorized repair center there that repairs or sells parts:

Mr. Bob Manthey

Ruangsangthai Ltd.

114 Moo. 14 Buriram - Phutthaisong Highway 2074

Chum Het, Muang Buriram 31000

Thailand

(66) 044-666-484 mobile 081-069-8324

email: [email protected]

Here's a copy of that IPL that Kong Yang sent to me:

WP-255Q3 IPL.pdf

If it doesn't cover your pump model contact them and ask them to email you that correct one. If you've never taken one apart before you might want5 to take it to a place that does pump repairs.

[wayned]

It looks like it item 17 that you will be looking. I think that the Q3 and QS pumps use the same parts. You'll have to remove the impeller from the motor shaft and remove the motor to access it.

[sandmike]

Gents, many thanks for your prompt responses.

Cheers, SM

Sent by carrier pigeon

[cliveshep]

Back to some of the earlier posts where voltage drops mean pumps cannot spin fast enough to hit cut-off pressure - may I be permitted to offer a possible "fix" to this, a little "Heath Robinson perhaps but probably workable.

I assume that the cut-off pressure switch is of necessity on the outlet or house side of the pump? In which case raising the pressure on that side would trigger the pressure switch and cause the pump to shut off? Looking at this low voltage problem sideways, a 12 volt pump with an in-built pressure switch connected to a car battery and picking up water from a small header tank could pump up the system on the house side via a NR valve (non-return) and thus fool the mains pump into thinking it had done it's job. Such pumps are fitted into boats (I used to build boats) and should be available in LOS. A relay operated via a time-clock on the mains could turn on the 12 volt system at 7.00 for a few hours and a trickle charger could keep the battery charged. These pumps will operate at up to 40psi and have their own pressure switch and are designed for long service life.