[RE-wrenches] Off-Grid Whole House RO

[david quattro]

I’ve had good experience with installing a five or 10 second delay on one
of the pumps. This way the pumps’ start-current spikes are staggered


On Thu, May 8, 2025 at 12:38 PM Jason Szumlanski via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Water pump is not my strong suit. I usually leave that up to the experts
> around here. Unfortunately, the experts are clueless when it comes to
> off-grid living. I have a client with a setup that is pretty unworkable.
> I'm trying to give him some general guidance.
>
> The setup uses a brackish water (might as well be salt water) very shallow
> well. It is about 3 ft underground for the water table. The RO system
> installer has a 1 HP 1.25 SF Century centrifugal surface pump drawing water
> from the well and pressurizing the inlet of a StaRite 1.25 HP booster pump
> designed for about 10 GPM at 150 PSI to run water through the RO system.
>
> Both of the pumps run simultaneously and continuously when producing
> water, and the water production is ridiculously low. I understand that RO
> production is going to be slow, but the amount of power these pumps are
> using is pure insanity. I have advised the client that, at a minimum, this
> system needs to be on a smart load circuit to run only when there is
> adequate battery capacity. The startup surgery is not a concern, but it
> does flicker the lights and it makes quite the racket.
>
> My thoughts are that the well pump is drastically oversized. The booster
> pump only needs 10 gallons per minute, and it has a suction head of 15 ft.
> I don't even know if the well pump pressurizing the booster pump inlet is
> required. I'm thinking we should be slow pumping water into an interim
> holding tank at least at the height of the booster pump. At a minimum, the
> well pump should be on a pressure switch with pressure tank so it can
> cycle.
>
> Can anyone give me some general guidance, and perhaps a VFD pump that does
> not have the startup surge and is maybe more efficient? During times of
> heavy use, the RO system can easily eat up half of the PV produced during a
> day at this site.
>
>
> Jason Szumlanski
> Florida Solar Design Group
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