That is what I was thinking, that the RO booster pump doesn't need a lot of pressure on the inlet side. There is a lot of wastewater, but I have not calculated the ratio. My visual analysis is that is it more like 6:1 or more. The production level is very low, perhaps 1-2 gallons per minute. I would love to not have a well pump running at all when producing RO, pumping raw water into a holding tank in advance of RO production. I don't think the owner is opposed to managing this manually, but it could also be set up on a solar direct DC pump or on a smart load output of the inverters if using an AC pump.
The house does have rainwater catchment that is great in the summer, producing 100% of its needs. However, the property is more heavily used in the dry winter months. So the rainwater system doesn't align with the use case for the home (vacation/second home in the nice season in Florida). Jason Szumlanski Principal Solar Designer | Florida Solar Design Group NABCEP Certified Solar Professional (PVIP) Florida State Certified Solar Contractor CVC56956 Florida Certified Electrical Contractor EC13013208 On Thu, May 8, 2025 at 3:22 PM Jay via RE-wrenches < [email protected]> wrote: > Hi Jason > > What’s the actual water output from > The RO? We had one at our house before I took it out and replaced the > house water with rainwater catchment. 3 yrs and counting in the high > desert. > I couldn’t live with the 2-3 to 1 loss ratio. > > A few options as I suspect the actual RO output is closer to 1-2 gpm. > 1. Use a 1/3hp well pump into a large pressure tank with relatively low > pressure switch. You might even get away with a small sump pump. The RO > should t need but minimal input pressure > > 2. Assuming the RO system doesn’t need rhe 1.25hp pump ( i am assuming > the RO goes into a tank and much then has a pressure pump to supply the > house. If it doesn’t I would recommend installing said design) I’d install > a smaller motor and pump head to better match the RO flow rate. > You could look at getting a high efficiency DC pump or 3 phase with vfd. > Sun pumps has such things. > > Jay > > > > > On May 8, 2025, at 12:38 PM, Jason Szumlanski via RE-wrenches < > [email protected]> 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 > > _______________________________________________ > > List sponsored by Redwood Alliance > > > > Pay optional member dues here: http://re-wrenches.org > > > > List Address: [email protected] > > > > Change listserver email address & settings: > > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > > > There are two list archives for searching. When one doesn't work, try > the other: > > https://www.mail-archive.com/[email protected]/ > > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > > > List rules & etiquette: > > http://www.re-wrenches.org/etiquette.htm > > > > Check out or update participant bios: > > http://www.members.re-wrenches.org > > > _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/[email protected]/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org > >
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