Which pump do I need?

I'm flipping back and forth about which pump to buy and whether or not to use a tank. IMO, I think I would be better with a pressure tank and slightly oversized pump. We are replacing a submersible pump with one that will mount on the pier in our lake. The submersible was installed with a pressure relief valve rather than a pressure tank so it runs continuously while watering the lawn. We are pumping out of a lake to about a 60 ft elevation. The furtherest away head is rougly 250-300 ft. There are at least 4 rotators on each zone. We have 120 volt wiring available. I'm thinking a 1 hp convertible jet pump would do the trick but I don't know enough about pumps to be comfortable with my decision nor whether a well pump or irrigation pump would make any difference. Here's the spec's on a pump I am tempted to buy. Would appreciate any advice including the size of pressure tank if appropriate for this application.

Product Depth (in.): 21.65
Product Height (in.): 13.38
Product Width (in.): 11.61
Adjustable Speed: No
Amperage (amps): 11.8
Corrosion Resistant: Yes
Discharge Flow 0 ft. @ 40 PSI (gallons/hour): 1200
Discharge Flow 15 ft. @ 40 PSI (gallons/hour): 648
Discharge Flow 25 ft. @ 40 PSI (gallons/hour): 522
Discharge Flow 40 ft. @ 40 PSI (gallons/hour): 438
Discharge Flow 50 ft. @ 40 PSI (gallons/hour): 888
Discharge Flow 60 ft. @ 40 PSI (gallons/hour): 300
Discharge Flow 90 ft. @ 40 PSI (gallons/hour): 120
Float Switch: No
Hardware Included: No
Head Pressure (ft.): 138.4
Housing Material: Cast-Iron
Inlet Connection: Threaded female
Jet Pump Product Type: Convertible
Maximum Pressure (psi): 56
Maximum Working Temperature (F): 77
Minimum working temperature (F): 35
Non-Clogging: Yes
Outlet Connection: Threaded female
Power Type Required: AC
Product Weight (lb.): 40.7lb
Pump Switch Type: Switchless
Returnable: 30-Day
Self-Priming: Yes
Thermal Overload Protection: Yes
Voltage (volts): 115/230
With Tank: No
Certifications and Listings: No Certifications or Listings
Manufacturer Warranty: 12 month warranty

 

Usually a 1 hp convertible may work almost as well as a 1/2 hp submersible. Why move away from the submersible pump? If water is coming out of the pressure relief, you could use bigger sprinkler heads. Or maybe your pressure relief is set too low.

 

For irrigation you do not want or need a pressure tank. You really want to use a irrigation pump which is nothing more than a centrifugal pump. Pressure switches are not used. All a pressure tank will do is take is make the pump run harder trying to pressurize the tank and irrigate. A tank will cause the pump to cycle way too often.

 

Simple answer is "because we want to".... The old pump died. It is in a recreational lake and since a girl died from ESD (electrical shock drowning) there has been a heightened fear of electrical wires in the water. So, the nearest thing to a safe solution and to keep the neighborhood happy we are going for an above water style pump.

 

I may have to think about that a while. I do not understand the logic of why a pressure tank would make the pump cycle any more than a system without a tank. IMO the system would always be charged and ready. Unless it is an oversized pump it will run continuously as long as the valves are open to irrigate the lawn. I've seen systems like this set up using a cycle stop valve which to me looks like nothing more than a PRV. I'd really like to know more so I can understand the logic of not using a tank.

 

A few years ago in Palm Beach County there was news stories about the electrical hazards with devices under water at docks with people getting shocked. About five years ago a child was electrocuted at a pool at one of the Disney resorts in Orlando. There seems to be different enforcement on this issue. I was just browsing through the NEC book a few days ago and a section for electric at docks are addressed.

With the your recent ESD I would just go with an irrigation pump. Unless you need spigots for garden hoses a pressure tank does nothing for an irrigation system. Using spigots off lake water is not desirable since it be too easy for someone to take a drink with a hose.

You may want to run 220v if you can. Pumps will run cooler and more efficient. Usually 1 hp and 1.5 hp can be either 120 or 220. From my experience the height and distance you have I would install a 1.5 hp irrigation pump. If it turns out you think you have too much pressure you can always conbine zones. Reducing zones allows less run time of the motor.

My last home had five zones on city water. I added a well with 1.5 irrigation pump and reduce the zones to four. One zone was only four rotors and the pressure was just right. I probably could have reduced it to three zones.

It’s only my opinion.

 

Good enough reason. You know to double the size, prevent suction leaks, pay attention to priming, and deal with the noise. You will still want to power your new pump via a GFCI. You will make sure the top of the pump is lower than 25 ft above the low water mark on the lake.

It is usually better to do your finer filtering after the pump. Your in-lake screen keeps out fish, weeds, etc. However size can compensate for fineness. Put your mesh around a cage to expand the area. Sucking water is harder than pushing water through a filter. Cleaning an above ground filter is usually easier than for an underwater filter.

 

This is true.... but I still do not want a submersible pump or electric wires in the water.

 

Nothing personal... but no matter what we are not using a submersible pump under any circumstances.

 

You would need a 25 amp circuit run with #10 wire. Do you have that available? Otherwise, it may be easier to run 24o.

Have you worked out the pressure and gpm that you think will be delivered to your "rotators" and compared those to the requirements?

 

This will be a replacement pump and I'm not sure of the type rotors on the system, actually not positive of how many either. Some Jack Rabbit has all the wires disconnected from the controller as well as outside the garage where the controller is located they are disconnected at the ground. I'll have to locate valves and wires and like have x-ray vision to see what is there and what is needed. I'm going on a lot of assumption but will take a lot of information from the current set up to re-design the system and calculate as needed. At this point, my only real option to make sure everything is operational other than the pump is to connect the system to the public water supply for testing. I do have a chat-r box and wire tracing capabilties (lawn mower and an AM radio). The pump does have a 10 gauge electrical supply and I assume at least a 20 amp breaker, probably a 30 amp.
The last system I designed and installed had a head of 35 ft, 8 gpm at 35 psi (measured with pressure gauge). It works flawlessly.

 

Thanks... Gould's GT10 is the one I've been considering. Their chart is a bit confusing.