Need assistance with residential pump selection

Need some assistance on pump selection for residential in our off-grid home. Since this is our only water source, high reliability is a prime concern.

Current specifications are as follows:

*15,000 gallon rain catchment tanks (3) 1 ½” pvc from bottom of tank (with foot valve at end of pipe) to house – 36 ft.

*Under slab to mechanical room 18 ft. in 1” Pex

*Total vertical rise - tank foot valve to pump location in house – 11 ft.

*Total horizontal run – tank to mechanical room – 54 ft.

*House will have 80-85 gallon Flexcon pressure tank with a drawdown of 27.6 to 29 gal.

*House piping will have 45 psi minimum pressure

*Calculated water usage – 40 gallons/day

Pump will run off the house PV array of 1.4 kV (with back-up generator), so low power consumption or short duration is required. We have the capability to run 120/240 AC or 24vdc. Low noise is also a factor, since unit will be mounted in mechanical room in house.

I have looked at the AC Shurflo pump, but doubt it's capability to do the job I need. I am now looking at Grundfos pumps, but am unsure which pump is right for the job. Will the Grundfos MQ series work with a stand alone pressure tank, or would the jet pumps be a better choice?

I would appreciate any help or suggestions you can offer in helping me choose the correct pump for this application.

Thanks!

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,784 admin
    Re: Need assistance with residential pump selection

    40 gallons per day is not very much water (or power to do the pumping)...

    Grundfos makes very nice (and expensive) pumps... How much flow do you really need 8+ GPM or would 4 be OK for a shower and sink?

    Also, why AC? -- You have the standby losses of an inverter (or you have to manual turn the inverter on/off).

    A smaller DC pump would probably be more efficient with your electricity. You probably would have to rebuild it every 1-3 years (depending on how much grit you have in your water)--So that would be a bit of a pain.

    I am not an expert in water pumping--but your large pressure/storage tank would seem to allow you to use a smaller pump for normal household use.

    Jet pumps tend to be way less efficient and may seriously impact your energy usage. Do you have a neighbor/existing setup that you can measure power/current usage and see how much power you really need?

    Are you planning on using the (hopefully) excess solar PV power to run other items in your home?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Need assistance with residential pump selection

    Simple 12/24 vdc Surflo should pull water up the 11' and put it into a 60 psi tank. Remember, it is always easier push water up the hill than it is to pull it up. Can you locat the pump at the tank? Do you have freeze issues?

    Another option would be the Shurflo 9300 submersible which will pump ~5 gpm into 50 psi all day, drawing ~9 amps.

    Both Surflos make some buzzing noise however. My 9300 submersible telegraphs it's buzz up the 3/4" pex line from 100' away and makes it sound like there is a motorcycle under the house,, but not in the house however, only a faint buzzing

    Tony
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