What happens if pump flow rate too high?

[Qwertyjjj]

I have a shallow well about 25ft deep and I'd like to water the nearby garden with a pump.
The pump would have to pump up around 10ft and then across 120ft of polypipe.
From a calculator that resistance means about an additional 15ft of loss so 25 ft head total.
It would be attached to a hosepipe, which is around 300GPH.
Problem is the pump has a much higher GPH at 0 feet, maybe 2000GPH.
Any smaller pumps will not pump up the height.
So, what happens if the flow rate is higher than the output?
Does the pump increase the pressure and burst connections as the extra water will have nowhere to go?

 

[Valveman]

The pump will just be cycling on and off repeatedly, which is not good for the pump. You either need to use as much as the pump can produce, or use something like a Cycle Stop Valve that will make the pump produce exactly the same amount as you are using. Either of these things will keep the pump running continuously while the hose is on, which is the best thing for the pump.

 

[Sponsor]

 

[Qwertyjjj]

It's difficult to calculate exactly due to the lift height, feet head...
10ft of height plus 100ft of length (15 ft loss).
But then I have soaker hoses at the end, which don't use much water at all so the flow rate is very low.
If I take a pump with a low flow rate, it will not lift the water the height required.

 

[Valveman]

The CSV will make a large pump act like a small pump when you need it to. But you do need to use at least 1 GPM to keep the pump happy and running continuously.

 

[Qwertyjjj]

The CSV will make a large pump act like a small pump when you need it to. But you do need to use at least 1 GPM to keep the pump happy and running continuously.

Is it just like a pressure switch connected to a mini reservoir?
How does the CSV valve shut off the pump - it has no electric cables?

Without it, what causes the pump to cycle off if there is a blockage or valve shut?

 

[Valveman]

The CSV does not cut off the pump, it has no electric connection. It just regulates the pressure once the pressure switch turns on the pump. If you have a 40/60 pressure switch, the CSV is usually set for 50 PSI. It just keeps the pressure at 50 PSI as long as you are using more than 1 GPM, and doesn't let the pressure get to 60 so the switch can shut the pump off.

The CSV can only close down to 1 GPM, because the pump needs 1 GPM to keep the pump/motor cool. When you finally turn off all the faucets, the 1 GPM still coming through the CSV has no place left to go except the tank. So then the tank is topped off at 1 GPM until the pressure reaches 60 PSI and the pressure switch shuts off the pump.

 

[Qwertyjjj]

The CSV does not cut off the pump, it has no electric connection. It just regulates the pressure once the pressure switch turns on the pump. If you have a 40/60 pressure switch, the CSV is usually set for 50 PSI. It just keeps the pressure at 50 PSI as long as you are using more than 1 GPM, and doesn't let the pressure get to 60 so the switch can shut the pump off.

The CSV can only close down to 1 GPM, because the pump needs 1 GPM to keep the pump/motor cool. When you finally turn off all the faucets, the 1 GPM still coming through the CSV has no place left to go except the tank. So then the tank is topped off at 1 GPM until the pressure reaches 60 PSI and the pressure switch shuts off the pump.

Ah. SO in fact I need a tank and pressure switch also? Probably for the garden, I could just use a pressure switch and tank?

 

[Valveman]

Yeah you need a pressure switch and pressure tank, just not a very large one. We normally use a 4.5 gallon size tank with a CSV. But the only way you can make a 2000 GPH pump run continuously without a CSV, is to always use 2000 GPH. The CSV will keep the pump running continuously as long as you are using more than 60 GPH.

 

[Qwertyjjj]

Yeah you need a pressure switch and pressure tank, just not a very large one. We normally use a 4.5 gallon size tank with a CSV. But the only way you can make a 2000 GPH pump run continuously without a CSV, is to always use 2000 GPH. The CSV will keep the pump running continuously as long as you are using more than 60 GPH.

Could I also just install a pressure switch (either hose end or pump end) that will sense when the tap is open and switch on the pump as pressure drops?

 

[Jadnashua]

No, unless the water being used matches exactly what the pump can produce, it would cycle on/off continually, and kill the pump quickly.

 

[Reach4]

From a calculator that resistance means about an additional 15ft of loss so 25 ft head total.
It would be attached to a hosepipe, which is around 300GPH.
Problem is the pump has a much higher GPH at 0 feet, maybe 2000GPH.
Any smaller pumps will not pump up the height.
So, what happens if the flow rate is higher than the output?

There are a lot of pumps that pump less than 300 gpm. Are you just letting the water flow freely at the output end, or is there some kind of nozzle involved?

If you want some pressure at the other end, I would look for a 1/2 HP pump, maybe 15 to 20 GPM.
http://franklinwater.com/media/111727/M1698_C1_Series_Sales_Sheet_07-14_WEB.pdf is one form.
Here are numbers for a particular pump in that size range.

http://franklinwater.com/products/s...ubmersible-pumps/c1-series-submersible-pumps/ would be another form factor.

If you are not shutting off the water flow with a valve, you may not need a pressure switch or pressure tank. The flow will determine the pressure, but it is important that you not block the flow for long while the pump is running.

Does the pump increase the pressure and burst connections as the extra water will have nowhere to go?

Note that bottom "Shut Off PSI" number at the bottom? That would be the pressure the pump would produce if you totally blocked the water. No pipe will burst, and no hose should burst at those pressures. It is not OK for the pump to be in that condition for long due to lack of cooling, but the plumbing survives.

 

[Valveman]

Could I also just install a pressure switch (either hose end or pump end) that will sense when the tap is open and switch on the pump as pressure drops?

Again, a CSV will turn the 2000 gph pump you have into a 300 gph pump if that is how much you are using. You can do without a pressure tank and pressure switch if you want to turn the pump on and off manually. If you want the pump to come on when you open a faucet and go off when you close a faucet, you will need a pressure tank and switch. If you don't want the pump to continue turning on and off while you are only using 300 gph, then you need to add a CSV or buy a new 300 gph pump.