How To Choose A Water Pump

[PMK]

Hi,

I need to buy a water pump for a new two story home. The water supply is in an underground tank. What is my best bet for a pump - brand, model, wattage, or whatever?

The ones I've previously bought on the recommendation of the shops barely supply enough water to turn on the hot water heater upstairs. Is this normal?

Thanks,

Peter

[lopburi3]

If you want good water pressure highly recommend Grundfos water cooled pump, which is available at most places here. It costs about 12,000 baht but provides a good 65psi pressure and will provide good flow upstairs. It is also less noisy than the air cooled models. I previously had the largest Mitsubishi (405) but the Grundfos provides water through the normal wall heaters at hotel type pressure - which the Mitsubishi could not do.

[chownah]

To get better pressure from a cheap pump try installing the pump at a higher elevation. Usually people install the pump right at the tank since this makes the suction line shorter and less prone to leakage but a properly constructed suction line will not leak so this precaution is often not warranted. A pump with a pressure regulator will operate within a certain pressure range...usually not adjustable. For every metre that the shower is intalled above the pump you will be losing pressure. By installing the pump above ground level (second floor height is good or even higher is better) then you don't get so much pressure drop....you do, however need to stay within the manufacturor's specifications for the the height of suction lift.

Chownah

[lingling]

To get better pressure from a cheap pump try installing the pump at a higher elevation. Usually people install the pump right at the tank since this makes the suction line shorter and less prone to leakage but a properly constructed suction line will not leak so this precaution is often not warranted. A pump with a pressure regulator will operate within a certain pressure range...usually not adjustable. For every metre that the shower is intalled above the pump you will be losing pressure. By installing the pump above ground level (second floor height is good or even higher is better) then you don't get so much pressure drop....you do, however need to stay within the manufacturor's specifications for the the height of suction lift.

Chownah

...at the same time, the height a pump can suck water is much less than the height it can press. Check the pump specs so it is not placed higher (or near) the maximum suction height or it may wear out prematurely.

[Somtham]

If you want good water pressure highly recommend Grundfos water cooled pump, which is available at most places here. It costs about 12,000 baht but provides a good 65psi pressure and will provide good flow upstairs. It is also less noisy than the air cooled models. I previously had the largest Mitsubishi (405) but the Grundfos provides water through the normal wall heaters at hotel type pressure - which the Mitsubishi could not do.

Good info Lopburi but if you're going to install a pump that will deliver 65psi make sure you have plumbing and fixtures that can handle that pressure. If you have Thai standard plumping, faucets, toilets, etc you are going to spend a lot of time fixing leaks. I think around 40-45 psi will give you a good shower and less leak headaches.

rgds

[Silurian]

When I first looked at water pumps for a 3 story townhouse, I got all sorts of recommendations. I finally ended up choosing a Hitachi 280W pump. Most everyone I talked to stated it was probably too big. It delivers sufficient pressure for showers, etc. It wasn't all that expensive and works well.

[lopburi3]

Somthan:

That is possible but have been using 65psi in normal blue plastic/Thai fixtures for several years for five bath house. Had leak in first week which turned out to be the newest plumbing (typical work of cutting pipe short so joint not fit tight), but since then have not had any leaks. In any event have external pipes now so if/when will not be that big a headache. Not sure where you will find a 40-45psi pump as the shallow wells pumps seem to be below 35. Having enough pressure to allow more than one tap to be open and still continue showers is important when talking about extended family living; but probably not so much for a couple.

[Toni]

Hi,

I need to buy a water pump for a new two story home. The water supply is in an underground tank. What is my best bet for a pump - brand, model, wattage, or whatever?

The ones I've previously bought on the recommendation of the shops barely supply enough water to turn on the hot water heater upstairs. Is this normal?

Thanks,

Peter

As said in an answer: Grundfoss is one of the best and can be bought locally. The choice depends of from where you want to suck (altitude or depth), the height you want to pressurize and the amount of water you need in your house. These tables you can find in the specs before you make a choice.

Attention:

Suck with at least the same diameter of the outlet of the supply and never suck from the mains but use a storage-tank which is sufficient to meet your demands.

[PMK]

Guys,

Thanks for all the info. Where would I find the psi of the pump? Is that marked right on the pump, or is it calculated from various factors such as the height or depth of the water source, etc.?

Peter

Somthan:

That is possible but have been using 65psi in normal blue plastic/Thai fixtures for several years for five bath house. Had leak in first week which turned out to be the newest plumbing (typical work of cutting pipe short so joint not fit tight), but since then have not had any leaks. In any event have external pipes now so if/when will not be that big a headache. Not sure where you will find a 40-45psi pump as the shallow wells pumps seem to be below 35. Having enough pressure to allow more than one tap to be open and still continue showers is important when talking about extended family living; but probably not so much for a couple.

[chownah]

The puimp is turned on and off to regulate the pressure and it is controled by the pressure switch. You can find its on and off pressure settings in the specification section of the manual for the pump unit......and here when I say "pump unit" I mean a pump unit with a pump, motor, pressure regulator, and pressure tank.

Chownah

[Somtham]

Somthan:

That is possible but have been using 65psi in normal blue plastic/Thai fixtures for several years for five bath house. Had leak in first week which turned out to be the newest plumbing (typical work of cutting pipe short so joint not fit tight), but since then have not had any leaks. In any event have external pipes now so if/when will not be that big a headache. Not sure where you will find a 40-45psi pump as the shallow wells pumps seem to be below 35. Having enough pressure to allow more than one tap to be open and still continue showers is important when talking about extended family living; but probably not so much for a couple.

Lopburi - I'm tired of the city water outages and low pressure and am going to give a go at a sand filter and the Grundfos pump for the house water. Do you have a model number for the pump and does it have a selfcontained pressure tank?

Thanks

[Naam]

"but if you're going to install a pump that will deliver 65psi make sure you have plumbing and fixtures that can handle that pressure. If you have Thai standard plumping, faucets, toilets, etc you are going to spend a lot of time fixing leaks. I think around 40-45 psi will give you a good shower and less leak headaches."

*****

i second that wholeheartedly! in fact i have two pumps (with differently adjusted pressure switches). one running at 38psi and the second one kicking in at 34psi. no flow problem opening all taps in four bathrooms.

one caveat though. my home is only single story!

[elkangorito]

There is one other thing that may be worth considering & that is the amount of stops & starts the motor does in an hour. Whilst this figure mostly relates to large electric motors, it's not without its importance with motors in general.

If the pump is too big for the demand, its stop/start cycle will be very short (2-3 seconds on then 2-3 seconds off). This has 2 effects;

1. Every time a motor starts, it uses 6 to 8 times its normal run current, which costs the consumer more money.

2. Motors need to run for a fair while after starting to dissipate the heat created by high starting currents. As you can imagine, a motor that has a high stop/start frequency will get quite hot if it's not allowed to run for an extended period of time. This excessive heat will shorten the life of the motor.

Speaking electrically, the ideal size of a pump should be that it has a big enough air bladder (if this variety is used) so that water pressure is constant for a relatively long period (motor doesn't run). Conversely, the pump should be small enough to take a relatively long period of time to pressurise the system, allowing the motor to run longer (& cool off).

Then again, if money is not a problem, don't worry about these things.

[chownah]

There is one other thing that may be worth considering & that is the amount of stops & starts the motor does in an hour. Whilst this figure mostly relates to large electric motors, it's not without its importance with motors in general.

If the pump is too big for the demand, its stop/start cycle will be very short (2-3 seconds on then 2-3 seconds off). This has 2 effects;

1. Every time a motor starts, it uses 6 to 8 times its normal run current, which costs the consumer more money.

2. Motors need to run for a fair while after starting to dissipate the heat created by high starting currents. As you can imagine, a motor that has a high stop/start frequency will get quite hot if it's not allowed to run for an extended period of time. This excessive heat will shorten the life of the motor.

Speaking electrically, the ideal size of a pump should be that it has a big enough air bladder (if this variety is used) so that water pressure is constant for a relatively long period (motor doesn't run). Conversely, the pump should be small enough to take a relatively long period of time to pressurise the system, allowing the motor to run longer (& cool off).

Then again, if money is not a problem, don't worry about these things.

These are good considerations for choosing a pump...but what I'd like to find is some information about the practical effects of these things. Do you have a web site link that talks about actual numbers for these types of issues?

Chownah

[elkangorito]

There is one other thing that may be worth considering & that is the amount of stops & starts the motor does in an hour. Whilst this figure mostly relates to large electric motors, it's not without its importance with motors in general.

If the pump is too big for the demand, its stop/start cycle will be very short (2-3 seconds on then 2-3 seconds off). This has 2 effects;

1. Every time a motor starts, it uses 6 to 8 times its normal run current, which costs the consumer more money.

2. Motors need to run for a fair while after starting to dissipate the heat created by high starting currents. As you can imagine, a motor that has a high stop/start frequency will get quite hot if it's not allowed to run for an extended period of time. This excessive heat will shorten the life of the motor.

Speaking electrically, the ideal size of a pump should be that it has a big enough air bladder (if this variety is used) so that water pressure is constant for a relatively long period (motor doesn't run). Conversely, the pump should be small enough to take a relatively long period of time to pressurise the system, allowing the motor to run longer (& cool off).

Then again, if money is not a problem, don't worry about these things.

These are good considerations for choosing a pump...but what I'd like to find is some information about the practical effects of these things. Do you have a web site link that talks about actual numbers for these types of issues?

Chownah

No website to link to Chownah, however, the actual numbers are minorly important here because the behaviour of squirrel cage induction motors is relatively consistant throughout the various sizes.

If you wish, you could try to measure the starting current of a motor under load but it would be exactly what everybody predicts & that is, somewhere between 6 to 8 times the full load current.

As you may know, the life of an electric motor is reduced by such things as;

1. excessive heat (places the windings insulation under stress, allowing them to 'break down' at lower voltages).

2. abnormal vibration.

3. supply variations & quality (including harmonics on the supply & harmonics generated by VSD's etc).

If a motor has an insulation class of F or greater, it is designed to tolerate (without reduction of life) high winding temperatures generated by such things as harmonics &/or higher ambient operating temperature.

Cheap motors may not even state an insulation class on the rating plate, in which it's a 'guessing competition' when motor cooks. Most reasonable size motors these days are minimum Class F due to the amount of inverters being used with them, which is why these motors are often referred to as 'inverter duty' motors.

If your motor is less than about 2.2kW, I wouldn't worry about all this stuff.

Edited February 22, 2007 by elkangorito

[elkangorito]

I've found a website that seems to provide good general info about motors (it quotes standards & is not just some blurb from an unknown person). The URL is;

http://www.iprocessmart.com/leeson/leeson_...ure_article.htm

The below paragraph is an excerpt from the above website:

"Often overlooked as a cause of overheating is the number of start-stop cycles per hour. While starting, a typical motor draws five to six times the rated running current. This starting current accelerates heating dramatically. Most continuous-duty motor designs are intended to do just that--- operate continuously. Though various provisions are made relative to loading and off-time, NEMA essentially limits a three phase continuous-duty motor to two starts in succession before allowing sufficient time for motor to stablize to its maximum continuous operating temperature. This is highly application-dependent, so its best to check with your motor manufacturer if you face a high cycle application. A custom design may be required."

[chownah]

There is one other thing that may be worth considering & that is the amount of stops & starts the motor does in an hour. Whilst this figure mostly relates to large electric motors, it's not without its importance with motors in general.

If the pump is too big for the demand, its stop/start cycle will be very short (2-3 seconds on then 2-3 seconds off). This has 2 effects;

1. Every time a motor starts, it uses 6 to 8 times its normal run current, which costs the consumer more money.

2. Motors need to run for a fair while after starting to dissipate the heat created by high starting currents. As you can imagine, a motor that has a high stop/start frequency will get quite hot if it's not allowed to run for an extended period of time. This excessive heat will shorten the life of the motor.

Speaking electrically, the ideal size of a pump should be that it has a big enough air bladder (if this variety is used) so that water pressure is constant for a relatively long period (motor doesn't run). Conversely, the pump should be small enough to take a relatively long period of time to pressurise the system, allowing the motor to run longer (& cool off).

Then again, if money is not a problem, don't worry about these things.

These are good considerations for choosing a pump...but what I'd like to find is some information about the practical effects of these things. Do you have a web site link that talks about actual numbers for these types of issues?

Chownah

No website to link to Chownah, however, the actual numbers are minorly important here because the behaviour of squirrel cage induction motors is relatively consistant throughout the various sizes.

If you wish, you could try to measure the starting current of a motor under load but it would be exactly what everybody predicts & that is, somewhere between 6 to 8 times the full load current.

As you may know, the life of an electric motor is reduced by such things as;

1. excessive heat (places the windings insulation under stress, allowing them to 'break down' at lower voltages).

2. abnormal vibration.

3. supply variations & quality (including harmonics on the supply & harmonics generated by VSD's etc).

If a motor has an insulation class of F or greater, it is designed to tolerate (without reduction of life) high winding temperatures generated by such things as harmonics &/or higher ambient operating temperature.

Cheap motors may not even state an insulation class on the rating plate, in which it's a 'guessing competition' when motor cooks. Most reasonable size motors these days are minimum Class F due to the amount of inverters being used with them, which is why these motors are often referred to as 'inverter duty' motors.

If your motor is less than about 2.2kW, I wouldn't worry about all this stuff.

So, now after raising these concerns you are telling us to just forget it!!!....it doesn't really apply to domestic pumps?

Is the extra power consumed by a rapidly cycling domestic water pump of significance or not? Will the rapid cycling appreciably reduce the life of the motor and if so what is an estimate of how much? I think that these are the two main concerns to consider when choosing a domestic water pump which is what the OP wanted to discuss. Can you give us your view on how important these are in terms of quantities or percents? For instance, since a pump uses more power during startup time can you give us an estimate of how long a pump draws 6 to 8 times as much current?...is it 10 milliseconds, 20? 30? 50? or 100 milliseconds? With this information I could produce estimates of the percent increase in power consumption based on cycle frequency.........etc. I'm just looking for some practical information on the seriousness of these issues.

Chownah

[elkangorito]

So, now after raising these concerns you are telling us to just forget it!!!....it doesn't really apply to domestic pumps?

Is the extra power consumed by a rapidly cycling domestic water pump of significance or not? Will the rapid cycling appreciably reduce the life of the motor and if so what is an estimate of how much? I think that these are the two main concerns to consider when choosing a domestic water pump which is what the OP wanted to discuss. Can you give us your view on how important these are in terms of quantities or percents? For instance, since a pump uses more power during startup time can you give us an estimate of how long a pump draws 6 to 8 times as much current?...is it 10 milliseconds, 20? 30? 50? or 100 milliseconds? With this information I could produce estimates of the percent increase in power consumption based on cycle frequency.........etc. I'm just looking for some practical information on the seriousness of these issues.

Chownah

Come on Chownah, be reasonable. It is a general rule of thumb to consider motors less than about 2kW in size, not worth the worry of maintenance...unless you really want to keep it for a long time. Not all water pumps for domestic use are small (2kW or less).

According to my rough calculations, a 2.2kW motor will use about 13kW if I assume 6 times FLA. I also assumed that it takes about 1 second to reach 80% of full speed, therefore I further assumed that 0.6 seconds would be the amount of time when starting current is applicable. The overall result is about an additional 0.22kW hours per day (6.6kW hours per 30 days), if started 100 times per day. This is obviously an insignificant figure if the motor is small & I'd also say that it is quite possible for such a domestic pump to start 100 times a day (in 24 hours), if not more times.

[chownah]

Sorry for my previous whiney post. I was typeing my post while you posted the link....thanks for that.

Chownah

[lopburi3]

Somthan:

That is possible but have been using 65psi in normal blue plastic/Thai fixtures for several years for five bath house. Had leak in first week which turned out to be the newest plumbing (typical work of cutting pipe short so joint not fit tight), but since then have not had any leaks. In any event have external pipes now so if/when will not be that big a headache. Not sure where you will find a 40-45psi pump as the shallow wells pumps seem to be below 35. Having enough pressure to allow more than one tap to be open and still continue showers is important when talking about extended family living; but probably not so much for a couple.

Lopburi - I'm tired of the city water outages and low pressure and am going to give a go at a sand filter and the Grundfos pump for the house water. Do you have a model number for the pump and does it have a selfcontained pressure tank?

Thanks

It is the Groundfos MQ 3-45 model. 1hp, 1,000w, 4.5A. I am not using an external pressure tank but only the built in coffee cup size pressure tank so when tap initially opens there is a short dead time for motor to start but we don't have a problem with that as pressure is very consistent once pump starts (it is only a split second). Pump is cool to touch as heat is transfered to water and unit is located in 2nd kitchen.

[Somtham]

Somthan:

That is possible but have been using 65psi in normal blue plastic/Thai fixtures for several years for five bath house. Had leak in first week which turned out to be the newest plumbing (typical work of cutting pipe short so joint not fit tight), but since then have not had any leaks. In any event have external pipes now so if/when will not be that big a headache. Not sure where you will find a 40-45psi pump as the shallow wells pumps seem to be below 35. Having enough pressure to allow more than one tap to be open and still continue showers is important when talking about extended family living; but probably not so much for a couple.

Lopburi - I'm tired of the city water outages and low pressure and am going to give a go at a sand filter and the Grundfos pump for the house water. Do you have a model number for the pump and does it have a selfcontained pressure tank?

Thanks

It is the Groundfos MQ 3-45 model. 1hp, 1,000w, 4.5A. I am not using an external pressure tank but only the built in coffee cup size pressure tank so when tap initially opens there is a short dead time for motor to start but we don't have a problem with that as pressure is very consistent once pump starts (it is only a split second). Pump is cool to touch as heat is transfered to water and unit is located in 2nd kitchen.

Thanks for the info LB and I don't need you to post a website to verify the model you have ;-) I've checked 2 shops here in KPP and neither one carries the Grundfos but there's another shop I will check and if they don't have it I'm sure they will order it from BKK.

To Elkangarito - If you are buying an integrated system with the pressure switch, bladder, and pump all in one unit then I would like to think that the manufacturers have figured out how to size the pump so you're not chasing the on off situation. Over time I've found the large Japanese suppliers (Hitachi, Mitsubishi, etc) to be very good with their engineering.

rgds

[thedivezone]

Suck with at least the same diameter of the outlet of the supply and never suck from the mains but use a storage-tank which is sufficient to meet your demands.

It is the Groundfos MQ 3-45 model. 1hp, 1,000w, 4.5A. I am not using an external pressure tank but only the built in coffee cup size pressure tank so when tap initially opens there is a short dead time for motor to start but we don't have a problem with that as pressure is very consistent once pump starts (it is only a split second).

I'm confused now, can i or can i not connect the Grundfos pump straight to the mains.

I need to boost the pressure from a storage tank that's mounted on the roof but doesn't supply enough pressure to fill the bath tub in any reasonable amount of time.

Thanks

Mike

[lopburi3]

A pressure tank is not a mains storage tank. I have two 1250 liter SS tanks linked together and pump from that. Pump pressure output will be 65psi + input pressure. At output of pump do not have a pressure tank but direct to house plumbing. Only use the built in cycle stopping facility of the pump itself.

Never pump directly from supply mains. Let mains fill a tank of some type and pump from that.

[thedivezone]

A pressure tank is not a mains storage tank. I have two 1250 liter SS tanks linked together and pump from that. Pump pressure output will be 65psi + input pressure. At output of pump do not have a pressure tank but direct to house plumbing. Only use the built in cycle stopping facility of the pump itself.

Never pump directly from supply mains. Let mains fill a tank of some type and pump from that.

Thanks for that !

Mike

[chownah]

Lopburi3,

Are you sure that it provides 65psi + input pressure? Most pressure switches switch the pump on and off to maintain pressure relative to atmospheric and are not affected by input pressure.

Chownah

[lopburi3]

This is a jet type pump. 65psi plus input pressure according to manual.

[chownah]

This is a jet type pump. 65psi plus input pressure according to manual.

Interesting....it is not controlled by a pressure switch except for a low pressure cut out...that explains why it adds 65 psi to the existing water pressure...because its upper pressure is not regulated by a pressure switch. It is the pressure switch which most pumps have which limits the upper pressure and keeps the pump (usually) from ever reaching its upper pressure limit. The information at Grundfos does however say that it is a centrifugal pump and not a jet pump.

Thanks,

Chownah

[Somtham]

Somthan:

That is possible but have been using 65psi in normal blue plastic/Thai fixtures for several years for five bath house. Had leak in first week which turned out to be the newest plumbing (typical work of cutting pipe short so joint not fit tight), but since then have not had any leaks. In any event have external pipes now so if/when will not be that big a headache. Not sure where you will find a 40-45psi pump as the shallow wells pumps seem to be below 35. Having enough pressure to allow more than one tap to be open and still continue showers is important when talking about extended family living; but probably not so much for a couple.

Lopburi - I'm tired of the city water outages and low pressure and am going to give a go at a sand filter and the Grundfos pump for the house water. Do you have a model number for the pump and does it have a selfcontained pressure tank?

Thanks

It is the Groundfos MQ 3-45 model. 1hp, 1,000w, 4.5A. I am not using an external pressure tank but only the built in coffee cup size pressure tank so when tap initially opens there is a short dead time for motor to start but we don't have a problem with that as pressure is very consistent once pump starts (it is only a split second). Pump is cool to touch as heat is transfered to water and unit is located in 2nd kitchen.

Thanks for the info LB and I don't need you to post a website to verify the model you have ;-) I've checked 2 shops here in KPP and neither one carries the Grundfos but there's another shop I will check and if they don't have it I'm sure they will order it from BKK.

To Elkangarito - If you are buying an integrated system with the pressure switch, bladder, and pump all in one unit then I would like to think that the manufacturers have figured out how to size the pump so you're not chasing the on off situation. Over time I've found the large Japanese suppliers (Hitachi, Mitsubishi, etc) to be very good with their engineering.

rgds

Danm, could not find the Grundfos here and nobody was interested in ordering it so I bought a pump from a Spanish company called ESPA. Checked their site and the pump seems to be equivalent to the Grundfos MQ3-45. Still stacking 1.2m rings for the sand filter and storage so I should get the results in another week or so when the system is finished.

rgds

Nam Pa-pa good-bye. Soon, I hope.

rgds

[Somtham]

Somthan:

That is possible but have been using 65psi in normal blue plastic/Thai fixtures for several years for five bath house. Had leak in first week which turned out to be the newest plumbing (typical work of cutting pipe short so joint not fit tight), but since then have not had any leaks. In any event have external pipes now so if/when will not be that big a headache. Not sure where you will find a 40-45psi pump as the shallow wells pumps seem to be below 35. Having enough pressure to allow more than one tap to be open and still continue showers is important when talking about extended family living; but probably not so much for a couple.

I got the sand filter and pump setup and running and bam. Blew out both toilet valves, the washing machine hose, and the sprinkler system for the orchids. Now I'm looking for a pressure regulator but cannot find one in Kamphaengphet. Does anybody know where to buy one with 1 inch inlet/outlets?

thanks

[lopburi3]

And in two years use I have not blown anything. Have both FluidMaster and normal cheap toilet fittings; have old cheap plastic and steel strap type feed hose; have spray on each (with control valve to lower flow); have used two washing machines, dish washer, garden hose and such. The orchard system might be a problem but probably a flow control valve would solve that.

I do have small (Italy made) control/shut off valves on just about every pipe but all except sprays are full on. But that might make a difference if you have not used them. They are very handy to have when you want to work on something and not turn all water off.