Calculating Pump Water Output.

[carlyai]

Pump specifications:

LuckyStar, PC-301EA, 300 W.

 

Jet:

Single Jet PSJ-50

 

TDH = Static ht. + Static lift + Friction loss

 

TDH = 0 + 7.5 m + 4.5 m

 

(The suction pipe length from the footer valve to pump inlet is 7.5m)

 

The friction loss is calculated with 2 pipe joiners and a 90 degree bend.

 

The water table is 2m more than the static lift.

 

Using the pump curve supplied for a single jet, the capacity should be about 22 litres/min.

 

With the pump operating for about 5 mins, I measured the rate to fill a 1 Litre container through a 10 hose, which was 7 secs or approx 9L/min

 

Why aren't I getting a capacity of 22 litres/min?

 

The capacity at the output of the hose does drop of from when I first turn on the pump to when I take the measurement.

 

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[bankruatsteve]

Try closing a valve on the output to 3/4 open.  You probably won't get full but maybe a little better.

[carlyai]

Try closing a valve on the output to 3/4 open.  You probably won't get full but maybe a little better.

Hi thanks, will do.

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[farmerjo]

Your trying to read off the very bottom of the pump curve.

Most pumps work best mid range of the curve. 

[carlyai]

Hi thanks, will do.

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I did that, and a little better. Will check litres/hr later.

I still would like the pump exAPerts to tell me where my theory calcs. are wrong. There's a lot of difference between what I calculate and what I get in L/min.

I have noticed a water leak in a pipe connection when the pump switches off, so will fix that.

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[bankruatsteve]

No expert but my experience with jet pumps finds them finicky.  I think the system needs to be full of water for best output.  If the output stop valve is close to the pump, you can hear the difference from full open to partially closed.  Maybe try closing it until it sounds best.

[Kieran00001]

25 minutes ago, carlyai said:

I did that, and a little better. Will check litres/hr later.

I still would like the pump exAPerts to tell me where my theory calcs. are wrong. There's a lot of difference between what I calculate and what I get in L/min.

I have noticed a water leak in a pipe connection when the pump switches off, so will fix that.

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If you've got leaks then you can't expect it to be running at perfect performance, perhaps you also have a leak somewhere else that you can't see that is drawing in some air.

[carlyai]

 
If you've got leaks then you can't expect it to be running at perfect performance, perhaps you also have a leak somewhere else that you can't see that is drawing in some air.

Yes correct. Will fix it...bit of a job but...leaking where it goes into the jet. I let the offsiders tighten those joints as were a real pain to get tight even with the thread tape.

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[Kieran00001]

1 minute ago, carlyai said:

Yes correct. Will fix it...bit of a job but...leaking where it goes into the jet. I let the offsiders tighten those joints as were a real pain to get tight even with the thread tape.

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Absolutely no chance it will work to full capacity with a leak on the jet, you're lucky you got it to work at all!  

[carlyai]

 
Absolutely no chance it will work to full capacity with a leak on the jet, you're lucky you got it to work at all!  

I didn't notice it as it didn't leak when the pump was on. It leaked when the pump stopped. Just noticed it while doing something else. My back's no good so the guys tightened that joint up and cracked the thread.

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[carlyai]

No expert but my experience with jet pumps finds them finicky.  I think the system needs to be full of water for best output.  If the output stop valve is close to the pump, you can hear the difference from full open to partially closed.  Maybe try closing it until it sounds best.

Hi, yes I've adjusted the valve for best I think.

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[Artisi]

The water table is 2 m more, are you saying the water table is 2m higher the the foot valve. 

How about a quick sketch, solves any misunderstanding. 

[Fruit Trader]

29 minutes ago, Artisi said:

The water table is 2 m more, are you saying the water table is 2m higher the the foot valve. 

How about a quick sketch, solves any misunderstanding. 

I am also confused with the 2m. Is the source capable of delivering 22L/Min was the capacity posted in an earlier thread?

[xtrnuno41]

Note the pipe diam is 30mm , if its smaller it will effect working abilities.

You dont mention a quick return valve in it, maybe (probably) its in the pump. If it is, is it working right?

It prevents from water flowing back in the well again and you ll have air in the pump and piping again.

Pumphouse and piping should be all filled up, no air in or coming in, no cracks in sucktionpiping, which will let air in.

[dotpoom]

Wow....

[carlyai]

The water table is 2 m more, are you saying the water table is 2m higher the the foot valve. 
How about a quick sketch, solves any misunderstanding. 

Sorry, here's the sketch and a couple more pics.
The pump outlet feeds about 5m underground to the tap, and about 10m hose. So about 15 m altogether.



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[carlyai]

Sorry, here's the sketch and a couple more pics.

The pump outlet feeds about 5m underground to the tap, ( underground pipe is 35mm dia.) and about 10m hose. So about 15 m altogether.

 

 

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The leak is between the black and blue screw connections.

 

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[Crossy]

Er, normally the jet is at the bottom of the bore. What you have is no advantage over a conventional well pump.

"Ye cannae change the laws of physics Jim".

 

 

And an air leak where you indicate is a guaranteed loss of prime

 

[grollies]

Carlyai, FJ has given you the answer, you should take the mid-range pump curve figure. Their website quotes 12l/min as an average figure so your 9l/min is within range (given your cracked pipe). Try measuring 10 litres against time to get a more accurate figure.

[carlyai]

Er, normally the jet is at the bottom of the bore. What you have is no advantage over a conventional well pump.
"Ye cannae change the laws of physics Jim".
 

 
And an air leak where you indicate is a guaranteed loss of prime
 

It is a single jet pump. I had the set-up you show in the diagram before, but was having trouble, so, as the water table is above 8m, and wanting to get rid of a 2 pipe system into the aquifer I changed it.


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[xtrnuno41]

14 minutes ago, Crossy said:

Er, normally the jet is at the bottom of the bore. What you have is no advantage over a conventional well pump.

"Ye cannae change the laws of physics Jim".

 

 

And an air leak where you indicate is a guaranteed loss of prime

 

Er, only a submersible pump is a jet pump in the whole, it works completely submersed in water, so very short suction pipe. 

[Crossy]

13 minutes ago, xtrnuno41 said:

Er, only a submersible pump is a jet pump in the whole, it works completely submersed in water, so very short suction pipe. 

Sorry, I don't understand. A submersible isn't a jet pump and can lift far deeper bores than either a conventional or jet pump.

 

Our OP has a jet pump with the jet / venturi above ground, no advantage over a conventional well pump (actually less efficient).

 

[carlyai]

Carlyai, FJ has given you the answer, you should take the mid-range pump curve figure. Their website quotes 12l/min as an average figure so your 9l/min is within range (given your cracked pipe). Try measuring 10 litres against time to get a more accurate figure.

Hi grollies, thanks. I've enclosed a pic of the single jet pump graph. Maybe I'm reading the graph wrong.
From the curve my total head is 12 m. Which puts the capacity at around 23 l/min.
If I go to the linear section of the curve for a capacity of 12 l/min, then the total head is more than 30 m, which is not my case.
So I shouldn't be using this pump? But it is a pump for single jet use up to 8m.
How say you?

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[Fruit Trader]

48 minutes ago, carlyai said:

Sorry, here's the sketch and a couple more pics.
The pump outlet feeds about 5m underground to the tap, and about 10m hose. So about 15 m altogether.



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Your foot valve is 7.5M down so why go with all this jet pump drama when a basic house pump will handle this shallow well.

 

 

 

[grollies]

7 minutes ago, carlyai said:

Hi grollies, thanks. I've enclosed a pic of the single jet pump graph. Maybe I'm reading the graph wrong.
From the curve my total head is 12 m. Which puts the capacity at around 23 l/min.
If I go to the linear section of the curve for a capacity of 12 l/min, then the total head is more than 30 m, which is not my case.
So I shouldn't be using this pump? But it is a pump for single jet use up to 8m.
How say you?

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The pump, at 750 litres per hour nominal, should be ok for your house. You are adding 10m of 3/4" (?) hose before measuring your pump capacity. There is another thread going somewhere, where the advice to increase pump flow is to gag-in the pump outlet valve to make the pump work better.

 

Restricting the flow from the pump outlet, whether by a valve or restricting the outlet pipe size will reduce the pump flow accordingly.

 

In a perfect world, you be correct in expecting the maximum figures from the pump curve but in the field, go with the manufacturers figures which are for your pump, 12 litres per minute.

[carlyai]

Sorry, I don't understand. A submersible isn't a jet pump and can lift far deeper bores than either a conventional or jet pump.
 
Our OP has a jet pump with the jet / venturi above ground, no advantage over a conventional well pump (actually less efficient).
 

In the beginning...the pump was bought for me by a caring wifey without my knowledge. Now I had a successful double jet pump set up that kept having problems (with the footer valve staying open), so the pressure was on to convert it to a single jet set up like all the farmers have. I did, but not impressed.
What I really want is to understand the maths of the set up for future reference.

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[Crossy]

Just now, carlyai said:

What I really want is to understand the maths of the set up for future reference.

Understood Carl, but don't expect the rated performance with a surface jet and an air leak.

[grollies]

3 minutes ago, Fruit Trader said:

Your foot valve is 7.5M down so why go with all this jet pump drama when a basic house pump will handle this shallow well.

 

 

 

A basic house pump needs a flooded suction, I.e. a tank to gravity feed the house pump.

 

I have 2 boreholes, one with a submersible pump, one with a pump similar to Carlyai's and a similar water table depth at 8m.

 

A house pump for boreholes is not recommended.

[carlyai]

The pump, at 750 litres per hour nominal, should be ok for your house. You are adding 10m of 3/4" (?) hose before measuring your pump capacity. There is another thread going somewhere, where the advice to increase pump flow is to gag-in the pump outlet valve to make the pump work better.
 
Restricting the flow from the pump outlet, whether by a valve or restricting the outlet pipe size will reduce the pump flow accordingly.
 
In a perfect world, you be correct in expecting the maximum figures from the pump curve but in the field, go with the manufacturers figures which are for your pump, 12 litres per minute.

Right, starting to get it. So regardless of the total head, and suction lift (as my specs are well within this range), I go for the middle of the curve rating and about 12 l/m. So if I got around that (as in 9 l/m etc, I should be happy?

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[carlyai]

Understood Carl, but don't expect the rated performance with a surface jet and an air leak.

I grant you I have to fix the leak (back willing), but do a double jet and a single jet both mount in the aquifer?
If so, why have the farmers around here got the same set up as me, or the single jet mounted near the pump?

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