PDA

View Full Version : Correct Pump to draw water from lake



lsc87
07-16-2007, 12:03 PM
I am trying to use clear, cool lake water to supply my 5 zone sprinkler system. First I had a 1hp shallow well pump that gave me 75% of the pressure I need. I was told (on another forum) that I had the wrong type of pump, so I got a 1 1/2 hp Wayne Sprinkler Pump. With that, I can't get ANY water to the sprinklers. I haven't ruled out a mistake on my part, but how much can you screw up? I had the 1hp pump working. The new pump has water in it to prime, and sounds fine, but won't push water into the sprinkler system.

I asked a local pump installer who sets up sprinkler systems. He says the sprinkler pump I just bought is for moving a large volume of water, not for pressure. He says the 1hp shallow well pump should work, and to change the sprinkler heads to accomodate the lower pressure.

So should I try to find a higher horsepower shallow well pump, upgrade to a deep well pump (don't know much about them) , or keep messing with the 1 1/2 hp sprinkler pump?

I'm using 70 feet of 1 1/4" continuous tubing from the lake to the pump, with a check valve at the end to maintain prime. Vertical lift from the lake to my basement is 6 feet. Then there's 3 feet of pipe, straight up, from the pump to the 3/4" sprinkler intake connection.

thanks
Doug

Mr_Pike
07-16-2007, 01:22 PM
I don't know if you have a pressure issue, as much as a flow issue.

Do you know what the output (GPM) of the jet pump was? And the combined output of your sprinkler heads?

It sounds to me like you might just need to downsize the nozzles of your zones, or increase the size of your pump and suction line.

Without knowing what "sprinkler" pump you have, you might have a booster pump, which is not designed for suction per say.

What kind of "Tubing" are you using for your suction line?

lsc87
07-16-2007, 01:42 PM
Here is the link to the 1 1/2 hp Sprinkler Pump:

http://www.waynepumps.com/prodlist.asp?pcode=WLS150


Here is the 1hp shallow well pump that gave me low pressure (the low pressure had nothing to do with the attached tank):

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47906

The 1 1/4" tubing came from Home Depot, 100 feet to a roll. It's for sprinklers as far as I know. I had been using 3/4" tubing, but the first 1hop pump was starved for water. I upgraded, and the sprinklers worked better, but still didn't have the pressure I get from the city water.

thanks for the help
doug

Wet_Boots
07-16-2007, 04:51 PM
If you specify the number and type of sprinkler heads, that might help. A 3/4 feed to sprinklers would be for about 10 gallons per minute.

The pump installer was correct. The 'Lawn Sprinkler' pump is for moving volume. Not for developing pressure. Stick with the original pump, and rework the sprinkers.

speedbump
07-17-2007, 08:01 AM
You don't have very good taste in pumps.;)

Even with the centrifugal you now have, even though it's not a pressure pump, it should still be able to lift water 6' and push it to the sprinklers. The difference between a jet pump and a self priming centrifugal is the jet. It has a nozzle and venturi that help it make more pressure than a centrifugal without a jet. By sending some of the water brought to the pump back through the nozzle and venturi, you lose volume and gain pressure. The opposite is true with the centrifugal which is a jet pump without the jet. bob...

lsc87
07-17-2007, 03:57 PM
So which pump do I need... the lower quality jet pump, would that do it? Go ahead Bob, close the deal!

thanks
Doug

speedbump
07-18-2007, 05:57 AM
If your talking about the two shallow well jets on my site, the lower quality SW series won't pump quite as much water or pressure as the SFH model. The SFH is easier to prime also, but that's a one time deal, so not so important. It's just a matter of choice. You should know which pump you need to handle your system. Do you know how many gallons per minute you will need for the zones?

I just reread your original thread. If your using 3/4" pipe to feed your zones your restricted to around 10 gallons per minute before the friction loss goes off the chart. In that case a 3/4hp jet pump would do fine. Either that or increase the pipe size to at least 1". You can only cram so much water through any given pipe size, so some head adjustments may be in order.

bob...

lsc87
07-18-2007, 09:25 AM
The company that installed the sprinkler heads says I needs 10-12 gallons per minute, at 40-50 PSI. Lift from lake to pump is 5 feet with a 70 foot pipe run. Then the pump has to push it up another 5 feet thru a 3/4" copper pipe for about 20 feet. Hope this helps.

thanks for the help
Doug

speedbump
07-18-2007, 11:34 AM
That might be stretching it a bit with the 3/4" pipe. That may be your whole problem. Don't look for that kind of pressure either with a small jet pump while doing 12 gpm, you will have to have a 3/4 or 1hp to get that kind of water and that much pressure.

bob...

Wet_Boots
07-18-2007, 11:35 AM
If the sprinklers were installed before the pump was put in, Boo Hiss. It's more customary to fit a sprinkler system to a water supply, rather than demand a supply that fits a system. If the system uses rotor heads, different nozzles can be installed in the rotor heads, and the required flow will be reduced.

A stronger pump might have issues with your choice of suction line, assuming you used black poly pipe. For a 70 foot suction run, you'd do best to use the flexible PVC tubing that can stand full vacuum, and inch-and-a-quarter is too small a diameter for a long run. Always better to be generous with the suction line, so it doesn't have a friction loss that interferes with pump performance.

By the way, the "120V, 8.5 amps, 60 Hz" spec on the Harbor pump puts some doubt on its motor's true horsepower. Maybe the info plate on that motor shows it to have a service factor of 1.0, or some lesser value than what is customary.

lsc87
07-18-2007, 02:26 PM
About the pump coming before the sprinkler system, right now the sprinklers are fed by city water, and I get plenty of pressure. I don't know the flow or pressure coming in from the street, however.

thanks for all the help
Doug

Furd
07-24-2007, 10:33 AM
I am the one that originally replied to Isc87's questions on the "other" forum. One of the first things that I suggested was that he increase the suction piping to nothing less than 1-1/2 inch piping yet he decided to use 1-1/4 inch piping.

I then suggested that he install a vacuum gauge on the suction of the pump and if the vacuum was greater than 10 inches that he add the 3/4 inch pipe that he previoulsly used in parallel to the 1-1/4 inch suction line. To my knowledge he did not try this.

I have a fair amount of experience with pumps and I also suggested that this was not the best pump for the application but that it may work. I did not reply after he ignored my suggestions.

sansdc
04-28-2009, 06:36 AM
I want to be able to draw water from the lake by attaching a hose or hand sprinkler for now. Later we will install a sprinkler system in the ground. But Must water now -- temporary pump died. What do we need?

tomm
04-28-2009, 06:55 AM
Your going about it the wrong way.

You gotta tell us the # of sprinklers you are running per zone along with brand and nozzle installed.

PSLawnService
05-16-2009, 09:37 PM
Have someone calculate the TDH (Total Dynamic Head) for your location.
This is a combination of GPM, vertical lift, distance, pipe material, and pipe diameter. Talk with your local irrigation professional. He should be able to calculate the TDH and make a pump recomendation. It very possibly will be a Centrifical 2 stage pump.

Thatguy
05-17-2009, 02:04 PM
Volume or pressure, who knows. . .?
You need to see the pump curve
http://www.engineeringtoolbox.com/pump-system-curves-d_635.html
and play that curve against all the factors already mentioned.

It's the same with HVAC fan curves and vacuum tube transconductance curves; use a graphical method to solve it.