Water Pump Types

[scorpio1945]

Building a new house. Getting ready to buy a house water pump. A salesmen the other day said I need one of the square, squat ones, not the less expensive taller round ones. He says the round ones pressure goes up and down a lot. Any validity to that?

Any lessons learned in installing tank, pump and filter from other builders?

[Nigelmartin]

You can use a pressure tank after the pump, this will prevent any changes in water pressure

[fredob43]

You can use a pressure tank after the pump, this will prevent any changes in water pressure

You don't really give enough info.

Have you got main's water, well, house, bungalow, how far does the water need to go from the tank how may take off's, ie showers tap's.

Regarding pump's any one's that are Japanese Hitachi are very good most have a 5 year guarantee. Don't what ever you do fit a Thai one as they will last 6month's if your lucky and they don't have a guarantee.

You will need to pay around 5,500bt for a 180 pump up depending on how much water you need for the house.

Edited June 2, 2012 by fredob43

[Pib]

Where the guy said the pressure goes up and down he's referring to the the pump turn-on and turn-off pressures...there will be an electrical pressure switch mounted on the pump tank/output manifold assembly with two wires connecting to it...one wire coming from the 220V supply and the other wires going to the pump motor...it just an inline switch (like a light switch) that is switched on and off by water/air pressure. The pump motor/manifold assembly is mounted on a small 15-20 liter pressure tank (a.k.a., booster tank). Lots of different water pump models out there which used different pressure settings/range but the settings/range of 2.1bar (30psi) and 2.8bar (40psi) seems to be a very common one for an average size household pump.

When the pressure switch senses the output pressure has dropped to 2.1bar the pump will turn on to bring the pressure back up to 2.8bar and then turn off...basically this oscillating pressure which averages out to 35psi...and although the pressure is varying up and down 10psi from pump turn off to turn on it's not really noticeable when taking a shower, running a tap, using a water hose, etc., due to the gradual pressure change and flow capacity. Usually with one tap running full blast such a pump setting on its small pressure tank will turn on for about 5 seconds, then turn off for about 5 seconds, etc....during those 5 seconds the pump motor is off the compressed air in the top of the pressure tank acts like a spring, pushes down on the water in the water which continues pushing water into your pipes...when that pressure drops to 2.1bar/30psi the pump motor turns on and rebuilds the pressure to 2.8bar/40psi. I have this type for my two story house....works fine.

The other type is the constant pressure type which usually don't have any pressure tank, except maybe a small liter bottle type, and when a tap is turned on, pressure drops, the pump immediately kicks on and basically continues to run until the tap is turned off. It does have a flow control valve which maintains the constant pressure which in turn usually keeps the pump motor continuously running. If may or may not turn off briefly while the water is running as it all depends on the pump's water flow capacity, whether the pump has a small/liter size pressure vessel or not, etc. But basically it runs the great, great majority of the time and turns off when there is no water flow required/it reaches a certain upper pressure.

The constant pressure pumps usually cost around 20% more than the other type that is basically a pump motor/manifold assembly that is mounted on top of small 10-20 liter pressure tank. But based on my years in Thailand, looking at what my Thai family and friends use, and neighbors in my large single family home moobaan, I would say 90% of the pumps are the type like I have....that is, a pump motor/manifold/booster tank. But I'm talking a single family home type environment; for condos/apartments I expect the constant pressure pump type is maybe used more than 50% of the time due to it's generally smaller size/can fit on a ledge easier/or even under a sink top.

Some folks don't like constant pressure pumps since they are running all the time when water is running and if you have small leaks they will briefly kick-on much more frequently than the other type since the other type has a pressure tank to store water under pressure when basically the constant pump type don't except maybe a small one liter size screw on bottle tank. Then other folks would prefer to hear the pump motor run continuously while water is running versus hearing the pump kick on and off while water is running.

And of course we have completely stand alone pumps connected to large pressure tanks...tanks about the size of an adult body...but these pump type operate on the same principle as the one talked about above which is the pump motor/manifold mounted on top of 15-20 liter pressure/booster tank.

[scorpio1945]

Where the guy said the pressure goes up and down he's referring to the the pump turn-on and turn-off pressures...there will be an electrical pressure switch mounted on the pump tank/output manifold assembly with two wires connecting to it...one wire coming from the 220V supply and the other wires going to the pump motor...it just an inline switch (like a light switch) that is switched on and off by water/air pressure. The pump motor/manifold assembly is mounted on a small 15-20 liter pressure tank (a.k.a., booster tank). Lots of different water pump models out there which used different pressure settings/range but the settings/range of 2.1bar (30psi) and 2.8bar (40psi) seems to be a very common one for an average size household pump.

When the pressure switch senses the output pressure has dropped to 2.1bar the pump will turn on to bring the pressure back up to 2.8bar and then turn off...basically this oscillating pressure which averages out to 35psi...and although the pressure is varying up and down 10psi from pump turn off to turn on it's not really noticeable when taking a shower, running a tap, using a water hose, etc., due to the gradual pressure change and flow capacity. Usually with one tap running full blast such a pump setting on its small pressure tank will turn on for about 5 seconds, then turn off for about 5 seconds, etc....during those 5 seconds the pump motor is off the compressed air in the top of the pressure tank acts like a spring, pushes down on the water in the water which continues pushing water into your pipes...when that pressure drops to 2.1bar/30psi the pump motor turns on and rebuilds the pressure to 2.8bar/40psi. I have this type for my two story house....works fine.

The other type is the constant pressure type which usually don't have any pressure tank, except maybe a small liter bottle type, and when a tap is turned on, pressure drops, the pump immediately kicks on and basically continues to run until the tap is turned off. It does have a flow control valve which maintains the constant pressure which in turn usually keeps the pump motor continuously running. If may or may not turn off briefly while the water is running as it all depends on the pump's water flow capacity, whether the pump has a small/liter size pressure vessel or not, etc. But basically it runs the great, great majority of the time and turns off when there is no water flow required/it reaches a certain upper pressure.

The constant pressure pumps usually cost around 20% more than the other type that is basically a pump motor/manifold assembly that is mounted on top of small 10-20 liter pressure tank. But based on my years in Thailand, looking at what my Thai family and friends use, and neighbors in my large single family home moobaan, I would say 90% of the pumps are the type like I have....that is, a pump motor/manifold/booster tank. But I'm talking a single family home type environment; for condos/apartments I expect the constant pressure pump type is maybe used more than 50% of the time due to it's generally smaller size/can fit on a ledge easier/or even under a sink top.

Some folks don't like constant pressure pumps since they are running all the time when water is running and if you have small leaks they will briefly kick-on much more frequently than the other type since the other type has a pressure tank to store water under pressure when basically the constant pump type don't except maybe a small one liter size screw on bottle tank. Then other folks would prefer to hear the pump motor run continuously while water is running versus hearing the pump kick on and off while water is running.

And of course we have completely stand alone pumps connected to large pressure tanks...tanks about the size of an adult body...but these pump type operate on the same principle as the one talked about above which is the pump motor/manifold mounted on top of 15-20 liter pressure/booster tank.

VERY WELL explained. Thank You

[Gary A]

I have one of each and I just had the motor rewound on the constant pressure pump. That is the pump with the small nitrogen accumulator on it. My other pump with the pressure tank is about 7 years old and has never had a problem. The pump with the accumulator constantly turns on and off. I wouldn't buy another one.

[Pib]

I have one of each and I just had the motor rewound on the constant pressure pump. That is the pump with the small nitrogen accumulator on it. My other pump with the pressure tank is about 7 years old and has never had a problem. The pump with the accumulator constantly turns on and off. I wouldn't buy another one.

Just as FYI and for clarification to others, that nitrogen accumulator is the small approx 1 liter size bottle-shaped tank I refer to in my earlier post...a mini pressure tank. Instead of air in it like in the type with the larger booster/pressure tank, it uses nitrogen versus air to help prevent rusting of the screw-on accumulator bottle/tank. If the nitrogen leaks out/is absorbed into the water due to a ruptured rubber bladder within the accumulator then a person just has a water-logged 1 liter size accumulator/booster/pressure tank.

Where as the other type of pump setting on top of the 15-20 liter booster/pressure tank has its air charge replenished by an air control valve...for most Mitsubishi models its an octagon shaped device that screws into the top of the booster/pressure tank with a small diameter hose coming out of the top of it to the water inlet side of the pump's manifold assembly. On some other manufacturers' models the air control valve is mounted/integrated into the manifold assembly. Since the 15-20 liter booster/pressure tank type are fairly thick medal I guess the humidity ladden air being replenished into the tank by the air control valve has little additional rusting effect especially since there is also water in the tank touching the steel tank walls...as the tank that is just steel with no rubber badder containing the water like a badder used in most small/1 liter sized screw-on accumulator/pressure bottles.

Since I've mentioned rusting, to date I've never seen any of the 15-20 liter tank pump types with a tank that has rusted from the inside out due to direct water contact with the steel tank since no bladder is used. Haven't seen any that rusted from the outside in either. I expect the other pump assembly components would die/be replaced several times before the heavy gauge steel would rust through. I know my pump is approaching five years of age, is exposed to rain, but still looks almost brand new on the outside due to the materials/coating/type of paint used in construction of the whole pump. But my pump has broke twice... I did have to replace the air control valve at approx the 3.5 year point (but I think this was a premature failure without going into details) and the electrical pressure switch at about the 4 year point. I replaced both myself...easy and fast to do....at around 700 baht parts-cost for each...actual Mitsubishi brand name parts. But just last weekend at an Amorn store I saw a generic pressure switch for 350 baht. Don't it always happen...after buying something you fine an identical/very similar item not too long after at a significantly lower price.

[lopburi3]

Our Mitsubishi 405 rusted from inside and had to replace tank (using relatively clean Bangkok water). But believe after more than 10-15 years service. And same pressure and air control value issues several times on consecutive 405 models.

[Gary A]

Both my pumps are HTC made in Japan. Both have had about seven year of usage. The pressure tank model has never had any parts replaced while the constant pressure model had the motor fail. I think it cost about 1,000 baht to have the motor rewound.

I also have a cheap Thai made pump that is seldom used. The inside of the pressure tank is obviously rusty because after sitting a couple of days the water runs rusty for a few minutes. I think the HTC pressure tank has a rubber bladder or maybe a liner inside. Never any rusty water.