[RE-wrenches] Off-Grid Whole House RO

[drake.chamberlin at redwoodalliance.org]

Is using roof water and a cistern out of the question?

_Drake Chamberlin_

_Athens Electric LLC_

_Ohio Electrical Contractor's License 44810_

_NABCEP Certified PV Installation Professional_

---

On 2025-05-08 15:36, Jason Szumlanski via RE-wrenches 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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