I've got 2000 liters of stored water off caught off the roof of my shed (2 x IBC containers). These containers are situated about 0.5 meters off the ground but unfortunately the ground slopes upwards.

I intend to put in a small (350 watt / 0.5hp pump) with included adjustable water pressure regulator/dry run protection. (Link to pump I am considering) below the tanks.

Initially I intend to connect this to a hosepipe with the intention of putting in a simple irrigation system (which will probably have flow control valves for each feeder). I expect this system to water 2-4 times per day for a fixed amount of time.

I am somewhat price conscious as I'm doing this on a budget.

Do I need a pressure tank in this setup? (and also, do you see any problems with what I'm proposing to do)?

  • One way or another, you need to get pressure behind the water to move it uphill, overcome head (pressure) losses in the pipe runs, and drive it out of the irrigation system with some force so it goes where you want instead of just dribbling out. That can be calculated from the flow rate (LPM), pipe sizes and distances, elevation change, and irrigation head pressure requirements. There isn't enough detail here to do that, and designing the system is probably outside the intended scope of a question. (cont'd) – fixer1234 Nov 18 '18 at 9:33
  • If you have a local irrigation supply store with some knowledgeable people, they may be able to run the numbers for you. If your system is more or less a standard design, they may know from experience and rules of thumb what's required. In terms of pressure "hardware", any combination of pressure tank and/or pump could be used to provide all of the needed pressure. It would make sense to keep it simple, and go with the lowest cost single type of pressure source sized for the requirement. – fixer1234 Nov 18 '18 at 9:33
  • BTW, 2000 liters isn't much water for irrigation when you spread that over an area. You might want to run some calculations on water requirements and see if you need additional tanks. – fixer1234 Nov 18 '18 at 9:39
  • @fixer1234, I don't expect the elevation change to be significant in a pump situation - it's less then 1.5 meter rise - on a pump which can handle a maximum of 35 meter head. The main thing I'm concerned about is if the pump will cycle frequently while watering. – davidgo Nov 18 '18 at 9:40
  • @fixer1234 - assuming I use 40 litres per day (and that's very high for the vegetable garden, I'll probably use 20), that's 50 days of water - which is more then adequate in our climate. – davidgo Nov 18 '18 at 9:48

The key is the pressure regulator. Are you hoping to get a specific pressure of water to the irrigation system, with the regulator turning on and off as necessary? For example, might this pump supply a hose bibb that you can turn off? If so, then you will have to have some storage (a pressure tank) in the pressurized system or the pump will rapidly turn on and off as the pressure oscillates up and down.

If instead you can have the pump turn on and stay on for the duration, with the irrigation system set up so that it accepts whatever the pump gives it, then you need neither the regulator nor the pressure tank. You may actually want to disable the pressure regulator, because if the irrigation system stops accepting water (e.g. you turn off that bibb) and the pressure goes high enough to turn the pump off you'll get that rapid on/off/on/off again.

An alternative would be a pressure relief valve that would allow any excess water to dump back into the source tank. If you did have a relief valve, then you could still have a hose bibb, and turning off the bibb while the pump was on would merely waste some electricity.

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  • +1 for pressure relief valve dumping back to source. – fixer1234 Nov 19 '18 at 0:36

It turns out that no pressure tank was required The pump came with a flow controller attached which beautifully turns on the pump when there is a drop in pressure and stops when a high enough pressure is reached.

In practice this means that when I open the spray on my hosepipe the tap turns on immediately, and it turns 10-30 seconds after I close the spray.

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  • Interesting. Sounds like a) the pump doesn't mind straining against a blockage, and b) its controller waits for a period of high pressure before turning off the pump. Very cool, and thanks for posting the results. – Daniel Griscom Mar 24 '19 at 11:59

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