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Thread: Assistance needed in residential pump choice!

  1. #1
    DIY Junior Member RickNAZ's Avatar
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    Default Assistance needed in residential pump choice!

    Hello, My name is Rick and I need some assistance with a pump selection for residential use for 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 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 Shurflo AC (2088), but have doubts that it is powerful enough to do the job, as I am on the 'outer' limits of it's 9-12' capacity. I am currently looking at Grundfos pumps, but since I am new to this arena, I don't know all the answers! Will the Grundfos MQ series work with a stand alone pressure tank, or would the jet pump series be a better choice?

    I am open to and would greatly appreciate any advice, ideas and suggestions that you may be able to offer.

    Thanks!

  2. #2
    General Engineering Contractor ballvalve's Avatar
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    I would look hard at starite s.t.e.p. "motor over" cistern pumps. They claim very high efficiency and you can get 120 or 240 volts. The prices are amazingly small for a motor over pump [apparently the first on the market] and can be run on a small inverter.

    I believe a site called worldwide power and pump in Florida will come up on your search and give you a good start. The shurflow is weak on life span, and the grundfos absurdly high in cost. If you use it, please post back because it looks like a great piece of work for storage tanks and DC converter app's.

    Notice that this pump would be set IN your tank, and pushing water out is much more efficient than any suction based pump.

    At 40 gallons a day, this 1/2 hp pump will run for just a few moments!

    I noticed noise concern: the pump set in the cistern will be noiseless and since you are offline, the huge advantage of a submersible pump should be very attractive, even if you need run a wire to the cistern and remove the footvalve [you get a free checkvalve in the pump head]
    Last edited by ballvalve; 09-06-2010 at 09:28 PM.

  3. #3
    AAW jimtum's Avatar
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    The grundfos MQ 45 does not need a pressure tank since it is a constant pressure pump. It is also very quiet and I just put one in today, they are good, however I am with ballvalve, whenever you can use a submersible pump, use one. Less troublesome and life expectancy is longer. As well as when you call out a well man to check it he is going to troubleshoot it quicker than a booster pump and replace it quicker and will have the pump on his truck. They are usually cheaper than boosters or jets. I like the berkley pump myself.

  4. #4
    Moderator valveman's Avatar
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    The Grundfos MQ is not a constant pressure pump. It uses pressure on and flow off, and it has a built in pressure tank the size of a baseball. The electronic board seems to be the main cause of failures. But they don't have a good track record. Here is a picture of a dumpster outside a supply house full of them. This is usally a good place to see what pumps are lasting, and that is not one of them. I prefer a standard jet pump, or a 4" submersible if possible.

  5. #5
    General Engineering Contractor ballvalve's Avatar
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    Exactly, and thats the LAST thing this guy wants on solar with 50 gallons a day use. 120 or 240 V submersible on the inverter.

  6. #6
    AAW jimtum's Avatar
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    Hey guys my supplier calls it a constant pressure pump and when we need pressure it does provide constant pressure and we have had no problem with them. I do agree with you that a submersible is the better way to go since they are less problematic overall

  7. #7
    Moderator valveman's Avatar
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    The MQ is just a flat curve pump. It just can’t build any more pressure so some people think it is constant pressure. This pump came out to replace the variable speed jet pump that Grundfos had for a short while, because it wouldn’t last either. The MQ’s haven’t been around for very long, and I have never seen one last more than about 3 years. With the built in baseball size tank, a small leak in the house will usually kill an MQ very quickly. It certainly won’t last 20-30 years like a lot of old style jet pumps do. The MQ's in that Dumpster are not very old.

  8. #8
    Homeowner Thatguy's Avatar
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    So your flow rate is 40 gals per 16 hour day is 2.5 GPH
    and your pressure is about 120' of head?

    Normal usage is 100 gals per person per 24 hour day.
    Last edited by Thatguy; 09-17-2010 at 12:48 PM.

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