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GripB
08-10-2004, 04:07 PM
Homeowner here wanting to know the pros and cons of having a lawn irrigation system installed/connected to my well? (tired of dragging *****ing hoses and sprinklers arround)

--10gpm well

--1/2hp Grundfos well pump

--Would like to sprinkler 40,000 s.f. of lawn

Please comment/question. Thanks in advance.

Mdirrigation
08-10-2004, 07:33 PM
Well you dont have to move hoses anymore.

jerryrwm
08-10-2004, 10:11 PM
Grip,

What is the pressure at the well head or pump? And what is the drawdown and recovery rate of the well?

You are going to need a boat-load of zones at the flow you have available. At 10 GPM you might be able to run 3 - 3GPM rotors or 4 - 2 GPM rotors at a time if the pressure is available, and you size the pipe properly.

It is still going to take a long time to water nearly an acre. It takes a bit over 27,000 gallons to put an inch on an acre.

You're gonna need a big controller!

Have you considered a couple storage tanks and a centrifugal pump? With a float switch, you could water a lot of area and not run out of water with the well refilling the tanks as your system ran. And your zones could be bigger and the controller smaller.

Jerry

GripB
08-11-2004, 05:42 PM
Originally posted by jerryrwm
Grip,

What is the pressure at the well head or pump? And what is the drawdown and recovery rate of the well?

You are going to need a boat-load of zones at the flow you have available. At 10 GPM you might be able to run 3 - 3GPM rotors or 4 - 2 GPM rotors at a time if the pressure is available, and you size the pipe properly.

It is still going to take a long time to water nearly an acre. It takes a bit over 27,000 gallons to put an inch on an acre.

You're gonna need a big controller!

Have you considered a couple storage tanks and a centrifugal pump? With a float switch, you could water a lot of area and not run out of water with the well refilling the tanks as your system ran. And your zones could be bigger and the controller smaller.

Jerry

Jerry,
Thanks for the reply. I'll try and locate the pressure at the well pump and the drawdown/recovery rate (I guess I'll contact my well driller). The lawn is 3 years old. It's a 70% rye 30% Kentucky Blue lawn and I was planning on aerating/overseeding with 100% Kentucky Blue this fall. I was prepared to spend a few G's on an irrigation system, but it sounds much more involved and much more than a few G's. Am I right? We are also concerned about potentially drying up our well.

irritek
09-07-2004, 05:47 PM
The pressure and GPM have very little to do with your design. of corse the pressure is good its off a pump prob.w/a 40/60psi pressure switch. As far as the GPM I have installed big systems w/4-5 heads per zone 7-10 GPM on a 3GPM Well. You will have to use a controll panell w/ programable delays such as Rain Birds esplx clock.and make sure you know the accurate replenish rate of the well. NOTE: The head pressure in wellhead should be equal to the operating pressure of zones. I recomend an good size pressure tank to extend the life of your well pump.

jerryrwm
09-07-2004, 06:51 PM
The pressure and GPM have very little to do with your design. of corse the pressure is good its off a pump prob.w/a 40/60psi pressure switch. As far as the GPM I have installed big systems w/4-5 heads per zone 7-10 GPM on a 3GPM Well. You will have to use a controll panell w/ programable delays such as Rain Birds esplx clock.and make sure you know the accurate replenish rate of the well. NOTE: The head pressure in wellhead should be equal to the operating pressure of zones. I recomend an good size pressure tank to extend the life of your well pump.


What??? You're gonna have to explain more in depth how you run a zone with 7-10 GPM on a well pump that does 3 GPM.

I'm also a little more than confused about the statment that pressure and GPM have little to do with design of an irrigation system.

Pressure tank is fine, but a good pump start relay will be better on the pump for many reasons, especially in the prevention of short-cycling.

Have I been missing something these past 20+ years?

Jerry

Fatheroftwo
09-07-2004, 09:03 PM
I believe I'd start with a bigger pump and a new well. Spend $$ here or in the yard with more pipe and Zones.

jgc8fan
09-07-2004, 09:38 PM
The pressure (PSI) will tell you what GPM a head will produce (usually a chart printed on the head label) The amount of GPM is additive like voltage in a circuit. You will subtract GPM for each head installed, so... If you have 60 PSI, and 12 GPM at the well head, and your sprinkler head operates at say 3 GPM at 60 PSI then you could probably put 3 of these heads on a zone, but the pipe you use will also restrict your GPM. I think at 60 PSI 1" PVC tops out at 15 GPM, and 3/4" at 12 GPM. And the reason I said 3 heads and not 4 is because you always want to leave a little in reserve so that the system doesn't strain or lag to start up... Even when the heads are pressurizing the timer on the controller is already ticking so the longer it takes a zone to pressure up is losing watering time. And... If all that didn't confuse you enough... The GPM the heads use depends on the spray pattern. So if you have a gear drive that draws 3 GPM @ 60 PSI with a 360 degree (full circle) pattern, and you were to adjust this pattern to 180 degrees (half circle) then you are only using 1.5 GPM @ 60 PSI on that head. Therefore... If you are not using full circle patterns (like on the edges of the yard) then you can sneak extra heads into the zone. :) Then comes the issue of whether to use poly tube or PVC pipe. ;)

And the answer to the original question is... Pros... fully automated watering... No dragging hoses... No worrys. Cons... Initial cost... Regular maintenence (cleaning filters on heads etc...)... Check your codes before trying to put one in yourself... Best to leave to the pros, or possibly wind up with code violations and fines. (speaking from experience on that).

GripB
09-07-2004, 10:34 PM
The pressure (PSI) will tell you what GPM a head will produce (usually a chart printed on the head label) The amount of GPM is additive like voltage in a circuit. You will subtract GPM for each head installed, so... If you have 60 PSI, and 12 GPM at the well head, and your sprinkler head operates at say 3 GPM at 60 PSI then you could probably put 3 of these heads on a zone, but the pipe you use will also restrict your GPM. I think at 60 PSI 1" PVC tops out at 15 GPM, and 3/4" at 12 GPM. And the reason I said 3 heads and not 4 is because you always want to leave a little in reserve so that the system doesn't strain or lag to start up... Even when the heads are pressurizing the timer on the controller is already ticking so the longer it takes a zone to pressure up is losing watering time. And... If all that didn't confuse you enough... The GPM the heads use depends on the spray pattern. So if you have a gear drive that draws 3 GPM @ 60 PSI with a 360 degree (full circle) pattern, and you were to adjust this pattern to 180 degrees (half circle) then you are only using 1.5 GPM @ 60 PSI on that head. Therefore... If you are not using full circle patterns (like on the edges of the yard) then you can sneak extra heads into the zone. :) Then comes the issue of whether to use poly tube or PVC pipe. ;)

And the answer to the original question is... Pros... fully automated watering... No dragging hoses... No worrys. Cons... Initial cost... Regular maintenence (cleaning filters on heads etc...)... Check your codes before trying to put one in yourself... Best to leave to the pros, or possibly wind up with code violations and fines. (speaking from experience on that).
"Con"...Initial cost. Ballpark range what should I expect to pay to irrigate 40K? And back to the top, our initial concern, is there a risk irrigating from our house well?
I would have a pro install and maintain this.

jgc8fan
09-07-2004, 10:52 PM
It all depends on your area, and the local rates... Around here a typical yard 1/2 acre lot runs about $2300 for a 3 zone system. It's not too bad actually when you think about the benefits.

Most houses around this area usually have wells installed just for irrigation. No problems, and their grass "seems" greener than irrigation from city water (no chlorine in the well water, and more minerals for the grass). The only risk I have seen is that if you have a lot of metals and sulphur in the well it can stain pavement and the walls of your house with a rust color. This can be solved by making sure your patterns are set to keep the water from spraying the house or pavement (you don't want to water there anyway). The heads will overspray from the head itself a bit, but if it's built to code then the heads should be far enough away from walls and pavement anyway (In FL heads must be 12" from walls, and 6" from pavement). Other than that... You should be fine... If you get stains (Yes... sometimes you may get stains on grass usually from heads that need the filters cleaned) you can always add a water filter at the well to take the metals out of the water before going to the system.

BTW... Just so you know... I'm not an irrigation tech, but I've done a few systems on the side, and am studying to take the test next year.

earthtool
09-08-2004, 02:14 AM
Ditto on Jeff.

Oh almost forgot....Poly is our favorite.

jerryrwm
09-08-2004, 02:31 AM
...., but the pipe you use will also restrict your GPM. I think at 60 PSI 1" PVC tops out at 15 GPM, and 3/4" at 12 GPM.

Just to clear up a common misconception. Pipe size does not restrict the amount of flow (GPM) If you put a 1 gal per minute in one end, you are going to get 1 gpm out of the other end. Likewise if you put 100 gpm in, you are going to get 100 GPM out. But there is going to be a considerable difference in pressure between in and out. What pipe does is reduce the pressure due to friction. The smaller the ID the faster water travels at a given GPM. For example 10 GPM in 1" Sch-40 pipe has a velocity of 3.7 ft/sec and a pressure loss of 2.4 psi/100'. If you drop down to 3.4" pipe the velocity at 10 GPM is 6 ft/sec and the pressure loss is 7.8 psi/100' To go one step further using 1/2" pipe at 10 GPM the velocity is no9.3 ft/sec and the pressure loss is now 22.5 psi/100'. We still have the same volume of water, but it better have one helluva pump at the inlet to overcome the pressure losses.

The reason we size pipe is to control the velocity to minimize the potential damage caused by water hammer. Industry standards recommend a velocity between 5 and 6 fps for a closed pipe (Mainline). At that velocity a properly solvent welded joint should not come apart. Laterals with many outlets (Heads) can withstand higher velocities. But this chages also as you get into larger pipe - 4" and larger. In the bigger pipe you better slow that water down and use plenty of thrust blocks!!


And... If all that didn't confuse you enough... The GPM the heads use depends on the spray pattern. So if you have a gear drive that draws 3 GPM @ 60 PSI with a 360 degree (full circle) pattern, and you were to adjust this pattern to 180 degrees (half circle) then you are only using 1.5 GPM @ 60 PSI on that head. Therefore... If you are not using full circle patterns (like on the edges of the yard) then you can sneak extra heads into the zone. :)

The GPM a head uses at any pressure is a function of the nozzle orifice. From the charts supplied by the manufacturer they will tell you what volume to expect from each nozzle size at various pressures.

If you are using Hunter, Rainbird, Nelson, K-Rain, Weathermatic, or any of the changeable nozzle gear rotors you need to use the proper nozzle for each pattern or you will have uneven precipitation rates. Using the example of a 3.0 GPM nozzle. If you use the same nozzle in the 360 head as you do in the 180 deg head, you have double your precipitation rate on the areas watered by the 180. If it takes two minutes for the full to make one revolution, the half circle has made two passes over 1/2 the area thereby applying twice the water as the full circle. And if you use the same nozzle on a 90 deg head the precipitation rate has quadrupled.

To properly apply even precipitation the nozzles need to be different sizes if you are mixing fulls, halfs, and quarters on the same valve. Use a 1.5 GPM nozzle for the quarter circles, use a 3.0 GPM nozzle for the half circles, and use a 6.0 GPM nozzle for the full circles and you will get even precipitation rates over the entire watered area.

Now if you use something like a Toro V1550, then the flow chages as the pattern changes, but you need to adjust those damn little gates on the turret. Not to step on anybody's toes, but does anyone use these PITA heads?


Make sure you know what the well is producing at drawdown level and the pressure at the wellhead, and design the system accordingly. Also remember to calulate any elevation changes from the well to the point of the highest head. You will lose 0.433 psi per foot of verticle elevation, and the pump needs to be able to overcome that also to be able to deliver the required water at the required pressure to the last head on the system. And that my friends is the most important head on the system. If the head that is the farthest away and the highest head on the lines work, then it stands to reason that every head back the other way should work.

Did I muddy the water? Hope this helps. Any questions drop me an email.

Jerry R
Tx Lic #1452
(getting to be one of the old mossy heads down here. I think the license numbers are somewhere over 12000 now!)

GripB
09-08-2004, 11:36 AM
1st off, thanks for everyones replies so far. I'm actually understanding the majority of the discussions here. Is everyone pretty much in agreement that I should have a dedicated well for irrigating 40K?