Waterpump problem

[rutteketuut]

Hi guys,

I have a 2000 liter water tank in the ground at my home. When the tank is full everything works perfect, two people can shower and I can flush a toilet at the same time without any problem. When the water level in the tank is lower, ( tank still for 60% filled or more) the pump stays on all the time and I have little pressure or no pressure at all. So I replaced the pipe complete with new valve and Teflon tape on connection with the tank. I thought there might have been a crack in the pipe and the pump was sucking air when water level low but apparently that wasn't the problem because problem not solved.

Can anybody help me out because I,m desperate. I checked the pump, motor and propeller are ok.

I've been having this problem for quite a while.

Thanks in advance

Rudy

[sipi]

It sounds like the pump is losing "suction head". A bit hard to explain in 5 words but if you google it you will understand. Basically the pump might be worn but not visibly. Perhaps a submersible pump might be a better replacement. They are not particularly expensive.

[Thorgal]

Can you provide pump specs ?

It's important to know if he's self priming or not.

For instance the latest pump models from Grundfoss are self priming (-10m). The previous ones are not (-1,2m). Physically you can't see the difference but it's a huge difference for underground applications with variable water level.

Edited March 14, 2015 by Thorgal

[ubonjoe]

Moved to the do it your self forum.

[KhunBENQ]

The outlet of the tank is nearly on ground level?

The inlet of the waterpump is on a higher level?

If so, I suggest you mount a "check valve" at the tank outlet, which prohibits water to flow back into the tank.

I have such an installation and it works fine even with the water level below the pump inlet.

You can ask in a home store/supply shop for a "check valve" spoken in English.

They seem to know the word (no generic Thai word available).

A typical 1/2 inch check valve ("swing check valve", less than 200 Baht):

(source: a blog in Thai language: http://senderblog.in.th/?tag=%E0%B8%A7%E0%B8%B2%E0%B8%A5%E0%B9%8C%E0%B8%A7)

Print the picture and show it to the staff. Available at about all DIY / home stores.

Edited March 14, 2015 by KhunBENQ

[rutteketuut]

The pump is an ITC V series HTC-175V. It's 8.5 years old.

The outlet of tank is near ground level, the inlet of the pump a bit higher,about 25 cm.

Thanks

Rudy

[sipi]

I am assuming 8.5 years old has done its share of work. It could be losing suction by pulling air through the seal or something tricky. I can't find a service blister-pack online but a new one is 5370bht.

[rutteketuut]

Yes it has done its share of work, I agree Sipi.

Thank you all for your replies.

[Thorgal]

Can you provide pump specs ?

It's important to know if he's self priming or not.

For instance the latest pump models from Grundfoss are self priming (-10m). The previous ones are not (-1,2m). Physically you can't see the difference but it's a huge difference for underground applications with variable water level.

Self priming at -10 meter is impossible. A simple physical rule. Even a tube filled with water. closed on the top and lifted from a water tank, with open end in the tank will have a (vacuum) space on top. When lifted more then 9.8 meter. The water will be boiling at the surface then.

Maximum height you can reach is 9.80665 meter, a bit depending on position from the moon, and other planets "close" by. This has nothing to do with pump specs.

Arjen.

Dear Moonwalker,

Did you contribute to the problem of Rudy ?

Cheers !

[sipi]

Can you provide pump specs ?

It's important to know if he's self priming or not.

For instance the latest pump models from Grundfoss are self priming (-10m). The previous ones are not (-1,2m). Physically you can't see the difference but it's a huge difference for underground applications with variable water level.

Self priming at -10 meter is impossible. A simple physical rule. Even a tube filled with water. closed on the top and lifted from a water tank, with open end in the tank will have a (vacuum) space on top. When lifted more then 9.8 meter. The water will be boiling at the surface then.

Maximum height you can reach is 9.80665 meter, a bit depending on position from the moon, and other planets "close" by. This has nothing to do with pump specs.

Arjen.

Dear Moonwalker,

Did you contribute to the problem of Rudy ?

Cheers !

What you are saying about pumping from more than 10mtrs suction is correct. However bore pumps can and do pump from much deeper that that by pumping water back down and through a venturi which sucks water into the suction line. You can pull water from incredible depths using this method. That is how bore pumps operate.

[sipi]

Just briefly Rudy. It does seem a common pump. So maybe inquire locally about getting a service kit fitted if possible. Might be cheaper than a new one if they are available.

[Thorgal]

For your information :

http://sakalai.tarad.com/product-th-1040891-อะไหล่ปั๊มถัง+HITACHI+ITC.html?lang=en

[Aussieroaming]

I agree with Sipi...the pump life might extend to 8 plus years but it's unusual for a seal kit to last that long. Also the impeller might look ok but may just be worn enough to lose efficiency when the suction head is decreased. Change the seals and wack in a new impeller.

[Beardog]

That many year I would bite the bullet & get a new pump. Chances are the impeller is worn & since the pump has been giving you problem I would just spend the 5000-7500 on a new pump & problem solved. They are not really made to go much past the warranty mark or else the companies go out of business.

[sipi]

Mechanical seal kits can be fiddly to fit unless you have done them before. 1 small scratch on the ceramic disc and it is wasted. Maybe best to get a new pump, unless there is a competent certified repair shop nearby.

[Beardog]

And when you take apart the pump housing if a bolt snaps you better hope you have a great set of easy outs taps & dies once that bolt replacement isn't in perfect you get the tiny leak that makes the pump cycle over & over. It can be very frustrating working in an already to tight area ask me how I know this.School of hard knocks!

[sipi]

How did you go OP?

[rutteketuut]

I just installed a new Hitachi pump today. Same problem, it wasn't the old pump. Could it be termites that eat my pipe in the ground.

I thought they liked wood....

[sipi]

I just installed a new Hitachi pump today. Same problem, it wasn't the old pump. Could it be termites that eat my pipe in the ground.

I thought they liked wood....

Bummer

[sanuk711]

it may be a to simple solution--but have you had your tank cleaned lately--properly ? (putting a guy / girl inside to clean it) The build up of mud even from a city water supply out here is quite bad after a while.

[Prapaexpert]

Or if you have a check valve already who is by wrong type?

Then the water can get resist to go from the tank to the pump.

[Anthony5]

The outlet of the tank is nearly on ground level?

The inlet of the waterpump is on a higher level?

If so, I suggest you mount a "check valve" at the tank outlet, which prohibits water to flow back into the tank.

I have such an installation and it works fine even with the water level below the pump inlet.

You can ask in a home store/supply shop for a "check valve" spoken in English.

They seem to know the word (no generic Thai word available).

A typical 1/2 inch check valve ("swing check valve", less than 200 Baht):

(source: a blog in Thai language: http://senderblog.in.th/?tag=%E0%B8%A7%E0%B8%B2%E0%B8%A5%E0%B9%8C%E0%B8%A7)

Print the picture and show it to the staff. Available at about all DIY / home stores.

My check valve is at the bottom of the suction pipe, not at the pump outlet.

[sometimewoodworker]

The outlet of the tank is nearly on ground level?

The inlet of the waterpump is on a higher level?

If so, I suggest you mount a "check valve" at the tank outlet, which prohibits water to flow back into the tank.

I have such an installation and it works fine even with the water level below the pump inlet.

You can ask in a home store/supply shop for a "check valve" spoken in English.

They seem to know the word (no generic Thai word available).

A typical 1/2 inch check valve ("swing check valve", less than 200 Baht):

(source: a blog in Thai language: http://senderblog.in.th/?tag=%E0%B8%A7%E0%B8%B2%E0%B8%A5%E0%B9%8C%E0%B8%A7)

Print the picture and show it to the staff. Available at about all DIY / home stores.

My check valve is at the bottom of the suction pipe, not at the pump outlet.

Then your problems are down to two possible choices (which really are 1)

1) the check valve is leaking

2) the pump is too high above the water level when the tank is half full.

One answer is simple, but not pretty. Install a ground level tank.

The other is use a submersible pump in the tank.

Pumps are good at pushing water but poor at pulling/sucking it.

[rutteketuut]

My problem is finally solved. I replaced the whole suction line, put a new pipe through the tank cover into the tank.

Thank you all for your help.