Will sprinkler valve work at <10 psi?

[grower]

Thank you folks for many helpful posts on well casing. Now I have a 4" PVC well, free flowing. Water pressure is about 7 or 8 psi. I wonder if this pressure will work with conventional sprinkler valves? I read somehwere that sprinkler valves need pressure for proper operation, especially closing. Please comment. Thank you.

[Bird]

Let us know what happens, because I'll be very much surprised if you find a sprinkler that will work with pressure that low. I don't really know what the "norm" is, but I would expect you to need at least 40 psi for satisfactory operation, with 60-80 psi being much better.

[jimbrown]

By sprinkler valve I assume you mean the valve that turns the water on and off. The answer is it depends on the type of valve. Some are just a switch and the water pressure actually opens and closes the valve. these will not work below about 25lb. Some actually open the valve with a motor or selioniod. Those will generally work at any pressure. Most impact type sprinklers require 25 psi or more to work but there are some low pressure ones that will work at 10 or 15 PSI. I have some RainBird ones that work at 10 PSI but they are all cheap plastic and break easy.

[GaryQWA]

Try this.
http://www.irrigationtutorials.com/pump.htm

Gary
Quality Water Associates

[grower]

Thanks for your replies. According to Rain Bird, their solenoid valves need minimum 15 psi. I suppose all sprinkler solenoids work the same.

[speedbump]

Another thing to keep in mind. If you use impact or popup type sprinklers, it takes a minimum of 30 psi to make them get any kind of coverage at all. Drip irrigation might work on lesser pressure.

I have about a thousand microjets that work fine with 18 psi. on my tree farm. But they only throw the water 1.5 feet.

bob...

[Pat]

Drip will work down to single digit pressures but you have to calibrate the metering as the manufacturer supplied numbers are way off at super low pressure. Watering times will be extended due to low flow. There are electric valves that work down to zero pressure as they don't use the water pressure to halp close the valve or hold it closed. I have some battery operated programable timers with valves like that.

Pat

[grower]

Please tell me where I can buy the electrical ones that stays open once opened, and stays closed once closed. Thanks.

[Pat]

Grower, the ones I have are built into small battery operated programable irrigatiion controllers I paid nearly $20 for at Orchelns or Tractor Supply but suspect Wally WOrld or lots of ploaces would have them. I should imagine you might be able to find other similar choices through professional nursery catalogs or similar searches.

These use a pair of AA cells and last for months and months. They do NOT depend on water pressure to assist in holding the valve tightly open or closed. I think they have small DC motors geared down and use limit switches to know when to stop opening or closing. If I were to use several of them in a commercial operation I'd either use rechargable batts (if too widely separated to make running wires practical) or run a low voltage line to them and supply the 3 VDC from a small power supply.

I haven't made any measurements but would guess that 18 ga wire would be OK for pretty decent runs. If you buy one of these and power it through a 100 ft length of 18 ga wire you can measure the voltage at the power supply (a couple AA cells or whatever) and then measure the voltage at the unit while the valve is changing state. If the voltage at the unit drops by more than about 10% you need a shorter run of wire or a larger diameter conductor like maybe 16ga. The 10% is calculated from the voltage at the PS while the valve is in motion and then again at the unit with the valve in motion (you can hear it if you listen carefully.)

Pat [img]/forums/images/icons/smile.gif[/img] [img]/forums/images/icons/smile.gif[/img]

[robertn]

You need a tank or pond, from which you can pump at higher pressure.

Not much of anything works at 15psi or below. Most pop-up spray heads need a minimum of 15psi, but like closer to 30psi(funny thing, pop-upspray heads don't like more than 30psi; over 30 psi they start to mist instead of spray, resulting in poor performance...).

If you try impact or rotors for longer range, they want a lot of water, at higher(ie 60-100) psi.

For drip, it will work at lower pressure; in fact it should be regulated below 20psi anyways. More than 20psi and you are asking to blow lines and barb fittings apart. The valves though, do not like to work that low for sure. In fact, many have a problem with low flow, much less low pressure.

there are some valves available that are a more positive on off. Rainbird makes a version. It is made more for remote area operation than for low pressure though. Most valves use the solenoid to turn on, but rely on water pressure to help turn them off. The other style valve uses a different, more expensive relay/solenoid. It actually turns the valve on or off, but does not rely on the solenoid to hold the valve open when turned on(typical solenoid has 24vac to it all the time when it is on)

Look at the Rainbird "Easy Rain" or "TBOS" setup. Other manufacturers make similar.