Pump for a small irrigation system with speed control

[Isetech]

I am looking for a small pump for a vegetable garden sprinkler systems.

It must has a bladder to reduce thumping (when it switches on and off).

It must some form of speed control to control the water flow or a some form of water flow management.

Any ideas?

[GCE]

I am looking for a small pump for a vegetable garden sprinkler systems.

It must has a bladder to reduce thumping (when it switches on and off).

It must some form of speed control to control the water flow or a some form of water flow management.

Any ideas?

You could use a VSD with digital pressure switch and leave the bladder out to offset cost

[Dylboy]

I don't know about irrigation but what is thumping and why does a bladder help ?

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[Isetech]

I don't know about irrigation but what is thumping and why does a bladder help ?

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If you are using a pressure switch to control the pump, If you dont have a bladder the pump will start and run for a second or 2, it will increase the pressure to a point that it will sometimes switch the pump off again, and so it just switches on/off on/off. The bladder absorbs the pressure.

One day if you ever go do a job which requires level control, the same thing will happen if your level probes hanging in the tank are too short. I got this down to a fine art at one stage, I spent many hours "commissioning" sites all over the country. Bad design and unskilled commissioning of water treatment plants results in what we referred to as thumping or the plant would full up the tank then stop and not restart.

[Dylboy]

Ahhh very interesting thank you ! Will do a bit of reading with that.

I have only ever replaced one floating level for a small 2000litre JoJo for garden irrigation.



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[Derlyn]

Those little pump/controller combo's that are sold at your nearest hardware store for jo jo tanks are very clever. They only have 1 setting and that is the "on" pressure setting.

After the pump has started, the circuitry then looks at the movement of the liquid through the controller. The pressure doesn't influence the turning off of the pump at all. As long as there is movement of the liquid through the controller, the pump will carry on running. You close the tap, when there is no more movement of liquid through the controller, the pump stops.

That is also how the "run dry" protection works on these units. Should there be no delivery to the pump, there will be no movement of liquid through the controller and the pump is turned off.

Clever nė.

Edit: 08.45am

I've just checked. The sensitivity of the controller as far as flow rate is concerned, is 1,5 litres/minute. So as long as there's a flow rate of 1,5 litres/minute or more through the controller, the pump will not switch off.

With these controllers, thumping is eliminated as the controller does not rely on pressure to turn off the pump. No bladder required.

[BobZA]

I am looking for a small pump for a vegetable garden sprinkler systems.

It must has a bladder to reduce thumping (when it switches on and off).

It must some form of speed control to control the water flow or a some form of water flow management.

Any ideas?

Not exactly sure what pressure control you wanting to do ... but maybe a timer could help out ? Delay switching on getting up to pressure (or other way around)

For pump speed control a VSD would be required. If just looking for a "soft start" to prevent a spike in pressure then maybe an electronic soft starter would do.

[SCW]

I think an electronic pressure controller is going to switch on and off too often if your irrigation system uses microjets as it will reach cut out pressure very quickly. The tank/bladder type controller will be your best bet, but even this will cycle a lot. As far as flow control, just install an inline ball valve and choke the output as this does not damage a centrifugal pump.