Irrigation pump question

[spaugh]

Is anyone using a seperate irrigation pump to pull from a tank or from a pond?  Not directly from a well? 

Im thinking of adding a dedicated irrigation pump to draw off a water tank and push water to sprinkler lines.  What I dont know is if I can do it without sprinkler valves?  Ideally the pump would get kicked on and it would just push straight to the nozzles and there wouldnt need to be a valve at all.  I just dont know if water will always want to run through the pump when not in use.  Because the water tank is at the highest spot on the property and all trees are downhill from there.  The pump wont need to do any lifting to prime itself.  I dont want a sprinkler valve in the equation if possible.  Ideas?

[cbss_daviefl]

If your tank is higher than the pump and output/spray nozzles, I think you need a valve. My pool pump is below my pool and it certainly requires shutting all the manual values to not gush water everywhere.  I believe above ground irrigation pumps rely on check values to prevent water from escaping downward when the water source is below the spray nozzles.  On the line from the tank, install a manual valve, then a solenoid sprinkler valve if the pump will be run on an automated schedule and keep the manual valve open, then the pump.

[spaugh]

How can I make it so that the pump wont run in case the solenoid fails?  Thats my main concern.  I dont want to have to put in pressure switches, bladder tanks etc.  I just want to push water to an open pipe and not have to add all the safeguard junk in case the sprinkler valve doesnt open when the pump is on.

Maybe theres a flow sensor I could use to switch on the pump relay.  Sprinkler timer goes on, water starts moving through the pump by gravity, then the flow sensor kicks on the pump?  Not sure the off sequence would work as well as the on sequence.

[spaugh]

Or maybe put one of those spring loaded pressure blow off valves in case theres a problem with the sprinkler valve.  Thats probably the simplest solution.  No extra electronics or sensors needed.  Just a mechanical safety pressure relief valve and a pipe run from it to dump into a drainage ditch. 

[slopat]

If the water source is higher than destination,  depending on flow rate desired,  you may not even need a pump. Regardless of pump or flow valve,  don't forget the vacuum relief right after to avoid the implosion!

If the water level can be used to determine the amont of water you want moved, tank or pond, a float valve can get it going and stop. Kind of like a toilet. Also, if  possible, flow and pipe friction can be taken advantage of. Once the water stars flowing and no air is in the line, the pipe can even be run to through the top of a tank -siphon.

Good idea on no electrically run or activated parts to make it simple.

[pineislander]

As you have described the system, water will run through the pump by gravity unless there is a valve closed in the line, there is clearance between the impeller and casing and the impeller itself can flow through the center and out the edge. You could close a valve wherever you want, on the suction or discharge size of the pump, and even much farther downhill. You will have to turn on the pump anyway, so will have to open the valve then start the pump. You could automate the valve and use a remote switch for pump. Normally, there should be a valve at the tank discharge which would allow pump and line maintenance without draining the whole tank. However, that valve could be left open in normal operation.
What you don't want to do is run any pump dry it can burn up the pump seal then other parts later on.
If there is any automation you plan to install be sure there is a low water shutoff at minimum because at some point the tank will run dry.

[spaugh]

As you have described the system, water will run through the pump by gravity unless there is a valve closed in the line, there is clearance between the impeller and casing and the impeller itself can flow through the center and out the edge. You could close a valve wherever you want, on the suction or discharge size of the pump, and even much farther downhill. You will have to turn on the pump anyway, so will have to open the valve then start the pump. You could automate the valve and use a remote switch for pump. Normally, there should be a valve at the tank discharge which would allow pump and line maintenance without draining the whole tank. However, that valve could be left open in normal operation.
What you don't want to do is run any pump dry it can burn up the pump seal then other parts later on.
If there is any automation you plan to install be sure there is a low water shutoff at minimum because at some point the tank will run dry.

yeah we have gate valves on the tank exits.  I have a 4" line that gravity feeds a fire hydrant for the fire truck to suck from.  And 2 two inch exits on the side of the tank.  I already have a pressure boost pump on one of the 2" outlets and its pressurizing all the pipes on the property currently.  It has a float switch to kill the pump when the tank goes low.  I will use the same signal on the new pump and do all the things you are saying for sure.  I just didnt want to put a bunch of extra stuff on this new pump.  Trying to keep the costs down, these projects get expensive quickly.  The new pump will do irrigation only on a 2 acre block of trees.  Currently the existing pump works well enough but my pressure drops on everything else when watering the big grove area.  And the existing pump is a 2 stage pump that makes higher pressure and less volume.  Im going to get a 2HP single stage pump for the irrigation that does less pressure and more volume.  they flow around 60gpm at 30psi.  I should be able to get 250 trees on one sprinkler valve.  The current setup is running 200 trees but its about all I can get out of it. 

[spaugh]

If the water source is higher than destination,  depending on flow rate desired,  you may not even need a pump. Regardless of pump or flow valve,  don't forget the vacuum relief right after to avoid the implosion!

If the water level can be used to determine the amont of water you want moved, tank or pond, a float valve can get it going and stop. Kind of like a toilet. Also, if  possible, flow and pipe friction can be taken advantage of. Once the water stars flowing and no air is in the line, the pipe can even be run to through the top of a tank -siphon.

Good idea on no electrically run or activated parts to make it simple.

I wish the tank was up a bit higher unfortunately theres not much elevation down to the grove.  Its only like 15ft down.  my house is lower than the trees and does still have about 20psi of gravity when the power is out.  its enough to shower with but not enough to irrigate with.

the tank has a 2" threaded hole already near the bottom thats currently plugged.  Im going to yank that and put a new pipe on that to feed to irrigation pump. 

these single stage irrigation pumps are not cheap.  around 700$.  Still half the price of my 2 stage booster. 

[Galatians522]

What about putting the pump on a raised paltform that is a couple inches above the tank? Then you don't need a valve. I suppose you could put in a check valve, but if it only has to lift the water a couple feet it probably wouldn't be necessary.

[spaugh]

What about putting the pump on a raised paltform that is a couple inches above the tank? Then you don't need a valve. I suppose you could put in a check valve, but if it only has to lift the water a couple feet it probably wouldn't be necessary.

I would but the tank is really tall and then I think it would still siphon out.  It seems like theres not really any way to avoid having a sprinkler valve in there.

[Victoria Ave]

A valve is necessary, don’t want to do this much work and half ass it.

How are you irrigating? I imagine with only 30 psi that it would be drip. You may need multiple valves to break those 250 trees into separate runs

[spaugh]

Valve wouldnt be necessary if the water source was below the orchard. 

Im using micro sprinklers.  They are rated for 15-30psi operating pressure and flow 15gal/hour. When irrigating large orchards with a pump, its more efficient to run at lower pressure. You get more gallons of water per watt of electricity.  All the micro sprinkler stuff is rated for under 30 psi. 

All of the micro irrigation is spec'd for flow rates at particular pressures.  Same with the irrigation pumps.  So its easy to design your system for a certain amount of trees and a particular pump and then size the micromsprinklers accordingly.  Or spec the number of trees and the sprinklers you want then size the pump accordingly.  Theres multiple knobs to turn. 

With the pump and microsprinklers I want to run, Ill be able to get 250-300 trees on this block and thats whats going to fit in that area.  And they can all be on at the same time. 

[cbss_daviefl]

You can use two solenoid valves connected to the same control wire so both operate simultaneously. Split the area so each valve controls a distinct area so you will know if one fails. This may also allow you to use smaller diameter pipe.

[brian]

How about a mechanical check valve with crack pressure higher than the "pump-off" pressure from gravity?  So the extra force of the pump opens it.  That is what I used for my fogging setup to avoid dripping when pump not running.  For me it was 30psi line pressure, 100psi valve crack pressure, 1000psi pump pressure.