Problem With Mitsubishi Water Pump

[JAS21]

Thanks for all suggestions. I now timed the pump with a faucet just after it and with that the pump runs 7 sec on and 6 sec off. I guess I will have to remove the shower faucet and see if there is something stuck somewhere.

As mentioned the house is one floor only. Due to how the pipes were laid there is a quite long distance from the pump to the house, maybe about 50 meter, all horizontal though so would that make a big difference?

Yes, even horizontal distance makes a difference due to friction and weight of the water. 50 meters is quite a distance for a small/low pressure pump. It's kinda like turning the water on at an outside tap and the water seems to rush out with good pressure and volume at the tap; but hook a 20 meter water hose to the tap and then the pressure/volume output at the end of the hose seems significantly less....well, it is due to water friction on the interior of the hose, weight of the water in the hose, etc.

It sounds to me that there is excessive resistance somewhere... lack of flow from the rain shower and pump not running all the time. So if you have taken the head off and the flow is no better look further back.

As Pib said 50M is a fair distance but if you used a reasonable dia pipe you should have been okay. If you have several bends then small dia pipe and bends would increase the frictional resistance.

I'm not that convinced about accelerating the water as once the water is flowing its only loss is frictional resistance.

I suggest that you cut into the pipe near the house and stick a vertical pipe say 2M high, run the pump and observe. Do the same near the pump end and compare the two. If much difference then you have a problem ... pipe too small dia, too many bends etc or something in it.

Of course it wouldn't surprise me if there was a stone wedged in the pipe somewhere. If that is the case only way is to work away from the pump ... cut the pipe and test the flow as you go along. you will need a few straights!.

[Phil Conners]

Sorry for not updating this topic, my bad.

Since my last post I did another test, opening 3 faucets in the bathroom (shower, bathtub and sink) and with that the pump runs continuously I think that indicates there are no serious problem with the piping between the pump and the bathroom.

I took the rainshower apart and there was a bit of yuk in one of the filters. After that was cleaned out the pressure was slightly better, but still far from what I'd like.

For some reason, when our house was built about 8 years ago, someone decided to run the water pipe underground all the way around the house. The pipe enters the property on the left side, follows the perimeter wall all the way to the back, all the way over to the right, all the way back to the front, before entering the house. Perhaps they had a reason, perhaps just TIT - in any case not much I can do about that short of digging all my tiles up and redo the piping at a considerable cost and hassle.

Would getting a stronger pump make more pressure? How strong would be enough for a serious rain shower?

[Pib]

Just upgrade to the next wattage model up...one that uses a pump turn on/off pressure in the 2.1 bar (30 psi) to 2.8 bar (40psi) ballpark, for an average 35psi pressure and you should be OK. Not only will the pressure be a little higher than your current model but it will have greater output volume capability. The 2.1/2.8bar cut-on/off pressure points is quite common on water pumps sold in this part of the world. On you can go with one of the more pricey Grundos-type water pumps which put out around 60psi. I use a Mitsubitshi WP255 in my two story house...provides plenty of pressure to the second story bathroom showers.

And remember, if using a hot water heater with your shower, the size of the heating tubes/coils the water must flow through is down around a quarter of an inch which restricts water volume/flow somewhat. The water volume coming from a shower head with its hot water tap wide open and cold water tap closed will be significantly less than if the hot water tap is closed and the cold water tap wide open due to the volume restriction caused by the smaller heating water tubes. Now you can bump up the pressure to overcome that, but I almost always use my hot water heater with the hot and cold taps adjusted to get very warm/almost too hot water from the shower, and my WP255 pump gives me good strong water volume from the shower head.

Here is Mitsubitshi water pressure/specs chart on its different models which might be helpful.

[Phil Conners]

Excellent input Pib! What a great source of information Thaivisa is. You'd almost wish the rest of the world had something like it.

[JAS21]

In addition to what Pib says.............

The fact that with three outlets the pump runs all the time shows excessive restrictions in the supply to the shower. A higher pressure will get more flow.

Just a thought ......... I guess that flexibles are in use, some flexibles have a very small internal diameter ... so take them off and check ..if you are unsure take them to your local pipework shop and see what they have ... normally two diameters are available small and not quite as small!.

Sometimes where the flexibles are attached the internal washers covers a lot of the hole ... undo and check.

'

Also you could ... run a bit of hosepipe from your water inlet to your shower and see what the flow is like ... you might need to 'Heath Robinson' a bit, but that will ... if the flow is then adequate ,,, let you know where the problem is!

[lopburi3]

You might want to review this thread from a few years ago - we still use the same model Grundfos pump and if you want a good shower pressure highly recommend (or other high psi capable pump). This runs 60psi plus and was a huge improvement over even the Mitsubishi 405 series pumps we used previously. There are newer model pumps available now and believe a good Chinese pump of same type is also available. Shallow well pumps do not provide good water pressure if you are used to western city water supplies.

http://www.thaivisa.com/forum/topic/323068-grundfos-mq3-45-pump/

[spirit47]

Anybody know about different between the Mitsubishi WP QS and Q3 series? I just bought a WP QS, because they say that this have "Non Toxic" colour in the tank, but this was for the Q3...

About Chinese Pump, after 2 years my first water pump from "Clinton", sounds english, but is chinese, rust through from inside to outside.

[lopburi3]

Chinese pumps are not all the same quality - suspect rust was the tank? That does happen but should be a longer life than that. Replacement tanks are available for most pumps.

[Beardog]

I also am having issues with my WP155Q3 - came home to find it running and over heating and no water out of the tap!! I pump from a well and have had no problems for 2 1/2 yrs. Found the tank dry ,so I primed it and got water flowing to the house ... But when you turn off the tap the pump cont. to run and Will not shut off!! A pressure valve issue??

I can press the spring under the round cap and it stops but as soon as I release it - she running again!!

Any help would be Great!! Can not find the book that came with it as far as trouble shooting issues.

We use it all the time as the village water is on and off so often, we found it best just to use the well.

If you have a well(not a borehole) you may want to check the foot valve on the bottom of the pipe in the well . If it gets impacted with dirt or debris it will have the same affect running the motor endlessly without shutting off ever. This happened to us when we first built our well & a lot of dirt clogged the foot valve . Had to clean a couple times till the well settled in but it remedied the situation.

[bangkokbrian47]

Hi All,

I've got a Mitsubishi WP 255Q3 fitted by the builder about 2 months ago and the pressure from all outlets is quite acceptable.

However, the pump cycles on and off once every 1 second when any outlet is open. Is this normal or is it too frequent?

Earlier posts seem to suggest that it should cycle about every 3-4 seconds. Have I got a problem I should worry about?

[JAS21]

Hi All,

I've got a Mitsubishi WP 255Q3 fitted by the builder about 2 months ago and the pressure from all outlets is quite acceptable.

However, the pump cycles on and off once every 1 second when any outlet is open. Is this normal or is it too frequent?

Earlier posts seem to suggest that it should cycle about every 3-4 seconds. Have I got a problem I should worry about?

Yes ... try draining the tank. Switch the pump off, shut the inlet and outlet valves, unscrew the drain plug remembering to not stand in front of it. After all the water has drained out, replace the drain plug.

[Pib]

Hi All,

I've got a Mitsubishi WP 255Q3 fitted by the builder about 2 months ago and the pressure from all outlets is quite acceptable.

However, the pump cycles on and off once every 1 second when any outlet is open. Is this normal or is it too frequent?

Earlier posts seem to suggest that it should cycle about every 3-4 seconds. Have I got a problem I should worry about?

Yes ... try draining the tank. Switch the pump off, shut the inlet and outlet valves, unscrew the drain plug remembering to not stand in front of it. After all the water has drained out, replace the drain plug.

Yeap, sure sounds like you have a waterlogged pump...that is, not the proper amount/enough air in the tank the pump/motor assembly is setting on.

Without the right amount of air in the tank to be compressed on top of the water then the pump will cycle on and off very fast like you have decribed...will be running around 90% of the time when a water tap is opened. This compressed air acts like an energy spring/cushion to push water out of the tank when the pump is not running...or said another way it helps the pump push water to your residence without the pump having to run all the time. I have a WP255 and with one tap wide open the pump will run approx. 5 seconds and then turn off for approx. 5 seconds.

After you drain the tank and be sure to let it completely drain because until it completely drains through the drain plug air can not get into the tank; no air in the tank...no energy spring/cushion can be created. If the pump cycle works properly after this draining procedure (i.e., "approx." 5 seconds on and 5 second off) then you need to figure what caused the pump to lose its air cushion. If the air control value (that six sided device screwed into the tank top with a small black/grey PVC hose running to the tank) is not working properly that can cause a loss of the air cushion/cause the tank to become waterlogged after a few weeks. Believe me, I know, as that is what happened to my WP255 once when the rubber diaphragm within the air control valve assembly ruptured with definition of a rupture being a very small tear in the diaphragm...but that's all it took...kinda like a pin hole sized leak in an intertube, a football, etc. I would drain the tank and it would work/cycle properly...then after a few days I noticed it was starting to run longer on each on/off cycle....then after a few weeks it was running most of the time...like only off for 1 second during each on/off cycle. Opened up the air control valve...saw the ruptured diaphragm...bought a new air control valve (couldn't buy just the diaphragm) for approx. Bt700...pump started working fine again....this happened about two years ago...the pump was around 3 years old at the time.

[bangkokbrian47]

Hi All,

I've got a Mitsubishi WP 255Q3 fitted by the builder about 2 months ago and the pressure from all outlets is quite acceptable.

However, the pump cycles on and off once every 1 second when any outlet is open. Is this normal or is it too frequent?

Earlier posts seem to suggest that it should cycle about every 3-4 seconds. Have I got a problem I should worry about?

Yes ... try draining the tank. Switch the pump off, shut the inlet and outlet valves, unscrew the drain plug remembering to not stand in front of it. After all the water has drained out, replace the drain plug.

Yeap, sure sounds like you have a waterlogged pump...that is, not the proper amount/enough air in the tank the pump/motor assembly is setting on.

Without the right amount of air in the tank to be compressed on top of the water then the pump will cycle on and off very fast like you have decribed...will be running around 90% of the time when a water tap is opened. This compressed air acts like an energy spring/cushion to push water out of the tank when the pump is not running...or said another way it helps the pump push water to your residence without the pump having to run all the time. I have a WP255 and with one tap wide open the pump will run approx. 5 seconds and then turn off for approx. 5 seconds.

After you drain the tank and be sure to let it completely drain because until it completely drains through the drain plug air can not get into the tank; no air in the tank...no energy spring/cushion can be created. If the pump cycle works properly after this draining procedure (i.e., "approx." 5 seconds on and 5 second off) then you need to figure what caused the pump to lose its air cushion. If the air control value (that six sided device screwed into the tank top with a small black/grey PVC hose running to the tank) is not working properly that can cause a loss of the air cushion/cause the tank to become waterlogged after a few weeks. Believe me, I know, as that is what happened to my WP255 once when the rubber diaphragm within the air control valve assembly ruptured with definition of a rupture being a very small tear in the diaphragm...but that's all it took...kinda like a pin hole sized leak in an intertube, a football, etc. I would drain the tank and it would work/cycle properly...then after a few days I noticed it was starting to run longer on each on/off cycle....then after a few weeks it was running most of the time...like only off for 1 second during each on/off cycle. Opened up the air control valve...saw the ruptured diaphragm...bought a new air control valve (couldn't buy just the diaphragm) for approx. Bt700...pump started working fine again....this happened about two years ago...the pump was around 3 years old at the time.

Hi Guys,

Thanks for your help.

I've now drained the tank and the pump is cycling correctly now - about every 4-5 seconds with one outlet fully open.

I will keep an eye (ear) open for any variance on the cycling time and if it reverts back to every second then I'll proceed with the further advice you've given.

Cheers.

[TexanTrev]

Hi Guys

Read through all of the above - very interesting. However it doesn't answer the problem I'm having. Pump is the tank type- problem is, works OK (?) for about 10 minutes, cycling on and off every 15/20 seconds. But them it stops working. After about 5 minutes it starts working again. It appears that the motor "stalls" -I've just checked the temperature of the motor and its very, very hot! This, it would appear, has been happening for some time(many months!). Any ideas please.

Cheers

[Pib]

Hi Guys

Read through all of the above - very interesting. However it doesn't answer the problem I'm having. Pump is the tank type- problem is, works OK (?) for about 10 minutes, cycling on and off every 15/20 seconds. But them it stops working. After about 5 minutes it starts working again. It appears that the motor "stalls" -I've just checked the temperature of the motor and its very, very hot! This, it would appear, has been happening for some time(many months!). Any ideas please.

Cheers

Sounds like it's overheating and the motor's built-in thermal protection device is tripping and then it resets after x-minutes which gives the pump motor time to cool down. Overheating can occur if the pump runs too long...like having an on cycle much longer than the off cycle....usually indicates a waterlogged booster tank. This overheating problem happen to me once when my tank got waterlogged and had an on cycle of around 10 seconds but an off cycle around 2 seconds. After about 30 minutes of running like this the pump would just stop running for approx 15 minutes and then start working again. After fixing the waterlogged condition the pump was back to an approx 5 seconds on and 5 seconds off cycle with one tap open full blast...motor stopped overheating and the thermal protection device built-into the pump motor stopped tripping.

Sent from my tablet

Edited July 26, 2013 by Pib

[jombom]

Hi Guys

Read through all of the above - very interesting. However it doesn't answer the problem I'm having. Pump is the tank type- problem is, works OK (?) for about 10 minutes, cycling on and off every 15/20 seconds. But them it stops working. After about 5 minutes it starts working again. It appears that the motor "stalls" -I've just checked the temperature of the motor and its very, very hot! This, it would appear, has been happening for some time(many months!). Any ideas please.

Cheers

Seems the pump might be air locking. Not easy to sort out --- you need to be patient.

[TexanTrev]

Thanks for the quick replies. I've drained the pump tank, checked the diaphragm for holes, refilled the tank. It now cycles 5 sec on, 15 off, with the tap fully open. The motor gets really, really hot eventually stops working - the motor STALLS, as it can be heard to be 'buzzing', and eventually the thermal cutout kicks in, stops buzzing. If you Tap the the pump body whilst it's buzzing, sometimes it will start working?

As has been said after about 15 minutes it starts working as the motor cools.

The pump (WP-105Q) is about 8 years old and has become more of a problem recently. The fact that the cycle times appear to be different to the quoted 5 sec on, 5 off is it still waterlogged? If so do I keep draining the tank, and try again??? Makes me wonder if the motor is knackered??

Any suggestions gratefully received.

T

[Crossy]

If the rotor is locking I would be looking at the bearings or something foreign in the pump chamber jamming the impeller, probably time for a visit to your local pump man with the pump.

May be easier to replace the beast.

EDIT It's possible that the start capacitor is on its way out (does it fail to re-start after an 'off' cycle?), a simple and cheap fix. Take it to the pump man.

[TexanTrev]

Yes I'm thinking along those lines - save all the hassle? There's nothing in the pump chamber, and the motor does turn when it's stalled (I've got burnt fingers to prove it!) and once it's cooled down the pump starts. Time to visit the local pump supplier me thinks.

Thanks for the response.

T

[Crossy]

A thought, before you shell on a new pump.

With the fan cover off the motor (so you can get at something that turns) run it until it fails. While it's buzzing, but before it overheats, try spinning the rotor by hand (carefully).

Does it start? If so replace the capacitor.

[TexanTrev]

Hi Guys, thanks for the responses. It appears the problem has been sorted. Took the capacitor off the motor (it smelt of burning), nipped down the local "pump" man. He said it was knackered, new one for 150 baht. Fitted new capacitor, and hey bingo it works. Motor runs cool, no stalling and that's after half an hour with the tapes fully open. Thanks Crossy that saved me circa 5k baht on a new pump.

Cheers T

[Crossy]

We aim to please, another satisfied customer

[TexanTrev]

[Pib]

Thanks for the quick replies. I've drained the pump tank, checked the diaphragm for holes, refilled the tank. It now cycles 5 sec on, 15 off, with the tap fully open. The motor gets really, really hot eventually stops working - the motor STALLS, as it can be heard to be 'buzzing', and eventually the thermal cutout kicks in, stops buzzing. If you Tap the the pump body whilst it's buzzing, sometimes it will start working?

As has been said after about 15 minutes it starts working as the motor cools.

The pump (WP-105Q) is about 8 years old and has become more of a problem recently. The fact that the cycle times appear to be different to the quoted 5 sec on, 5 off is it still waterlogged? If so do I keep draining the tank, and try again??? Makes me wonder if the motor is knackered??

Any suggestions gratefully received.

T

Glad you found the problem and got it fixed. Those start/run capacitors which are around 4 microfarad (uf) in size for these type pumps cost around 30 baht.. My Mitsubishi WP255 pump uses a 4uf start/run capacitor and I bought one about 6 months ago just to have as a spare...it cost 30 baht at Amorn.

Today while reading your post at my Mother-in-Law's house it struck me that you said your on-off cycle for your WP105 pump was 5 sec on and 15 sec off with one tap wide fully open....or said another way a 1 to 3 on/off ratio compared to my WP255 (a mid size pump) which has approx. a 5 sec on, 5 sec off or 1 to 1 on/off ratio with one tap fully on...a tap being feed by a half inch line.

I thought to myself maybe the smaller pumps (and yours is one of Mitsubishi smaller pumps) have a completely different on-off cycle due to their smaller motor/pump capacity and smaller booster tanks, but it seemed to me the on-off cycle for a smaller pump should be the reverse of what you mentioned...that is the on cycle time should be significantly longer than the off cycle time...maybe like 15 sec on and 5 sec off with one tap fully open.

As it turns out almost two years ago I installed in my MIL's house a new Mitsubishi WP85 (their smallest pump with smallest booster tank)...but it would still be very close to matching your WP105 and it may even physically look identical except maybe your pump rotor vanes being a little larger. I installed the WP85 when we had to evacuate our Bangkok home in late 2011 due to flooding and lived with the MIL for approx. 3 weeks....I just had to have some water pressure to shower with, wash the SUV, etc....plus I thought the MIL would like it which she did.

Anyway, I ran some tests today using that WP85. I first drained the booster tank to ensure it was not waterlogged since the MIL only turns in on occasionally; other times she continues just to use the low pressure from the soi water lines or dip her water for showers. Anyway, the only way I could simulate a 5 sec on and 15 sec off cycle was with one tap approx. 40% open....if I had it fully open the pump would run all the time. And the water line feeding the tap is a half-inch line.

With your pump now operating properly again and the motor spinning full speed, what is your on-off cycle with one tap fully open? I'm just wondering if the motor was not spinning at full speed before because of the faulty start/run capacitor and that somehow caused a run cycle that was predominately off---although it seems a slower spinning pump motor would just make the motor pump less water which means a longer on cycle...or quite possibly running all the time with a tap turned on. Then again, it could be the water line feeding the tap you used was a small line or hose...maybe even a quarter inch line/hose which would explain the on-off 1 to 3 ratio run time you reported since there was much less water flowing through a quarter inch line compared to a half inch line. Just curious what your on-off cycle is now with the pump fixed and what size water line is feeding your tap.

[TexanTrev]

Hi Pib

The capacitor was 50 baht (don't know where the 150 came from, finger problems when typing!!). The cycle time is 50/50 - 5/6 secs, so must have been something to do with the motor not running correctly with faulty capacitor? As a matter of interest, do these motors "eat" capacitors? Maybe something to do with the ambient temperatures?

Thanks for the information-it's good for future reference.

Cheers T

[Pib]

Hi Pib

The capacitor was 50 baht (don't know where the 150 came from, finger problems when typing!!). The cycle time is 50/50 - 5/6 secs, so must have been something to do with the motor not running correctly with faulty capacitor? As a matter of interest, do these motors "eat" capacitors? Maybe something to do with the ambient temperatures?

Thanks for the information-it's good for future reference.

Cheers T

I don't think they eat start/run capacitors at an abnormally high rate, but start/run capacitor do fail and they are used on many devices...usually anything using a motor. The capacitor probably just failed from old age, being hit many times during the day and night with starting up the motor, of course the quality of the capacitor would be a factor, and like you said high ambient temp is a factor. My WP255 pump is going on 6 years old with its original capacitor...I only bought a spare because the capacitor was dirt cheap and I wanted to have it immediately on-hand if/when it does fail...and you just know it will pick the worst time to fail.

Just a few months ago I changed the start/run capacitor on one of the mother-in-laws old metal blade ceiling fans...it had to be at least 20 years old...and I could tell the cap I replaced was the original. When it failed it would take the fan several minutes to get up to full speed and sometimes you had to give the fan a push to get the fan to started. After changing the capacitor you could actually see and hear a firm motor jerk when turning on the fan and within 10 seconds this airplane propeller sized fan was spinning at full speed. I also had a start/run capacitor on a central air conditioner outdoor compressor unit fan fail once (it was about 8 years old)...the fan just wouldn't start up but make a funny sound like it was trying but just couldn't get turning...changed the capacitor and it would startup/be running full speed within seconds.

P.S. I also have a spare pump "pressure switch" I bought at an Amorn store for around Bt250, because I've had the pressure switch fail once...the electrical contacts welded themselves together the pump would stop running...fortunately we were home at the time and was able to kill power to the pump within 5 minutes otherwise it would have run until the thermal cutout tripped....then after cooling off for around 15 minutes it would have kicked back on...and this cycle would have continued until the motor smoked itself. Of course it was a Saturday afternoon but I got very lucky in finding an exact Mitsubishi replacement for Bt700 at a store that sold all type of equipment and parts...it was there only switch in stock for my pump model. I have no doubt it will fail again over the coming years...but I'm ready with a replacement on-hand. Without a pump we can't get no water to the 2d story of our house (soi water main pressure ain't nearly enough) where the main bathrooms/showers...it just sucks if you can't refill the commode bowl after flushing or can't take a shower.

Yeap, I place priority on being able to repair my water pump quickly. But I have an even higher repair priority on my beer refrigerator....I've told the wife when it fails we'll have to immediately clear space in the main frig for my Chang beer.

Edited July 27, 2013 by Pib

[canuckamuck]

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

[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 ?

[jbrain]

First question not answered yet, but I'm generous and add another one already.

The small pump i'm talking about is used to pump the water from a concrete tank, in which my deep-well water is stored, through a Big Blue sediment filter and a resin filter to another clean water tank from which the house is supplied.

The pump is placed before the filter. No I have experienced several times problems where the pump get's blocked. This maybe because it's a cheap pump, but it also maybe because of sediment in the well water that corrodes/blocks the pump rotor .

Is it possible to place the pump after the sediment filter but before the resin filter, or maybe even after both filters ?

[canuckamuck]

No one has answered my question yet either Jbrain, but for your second question I would say the answer is yes - 'IF' the water flow from the outflow of the sediment side is sufficient to supply your pump.

Would the pump have to suck the water through the filter and up from the well (might be too much to ask)? Or does the water flow freely from the outflow of the sediment filter? Is the sediment filter a sealed unit that would allow a vacuum (suction)? and would sucking water through the sediment filter suck out the filter media?