4 gph on 75 gph RODI unit

[davefrombc]

RO/DI units are rated in gallons per day. 4 gallons per hour would come out to 96 gallons per day; so that unit is either outperforming its rated output, or there is a problem with the membrane allowing raw water to bypass it . Efficiency of RO units depends a lot on pressure . Up to its rated maximum, the higher the inlet pressure , the more efficiently a unit will run and deliver a higher percentage of RO water compared to waste water .
Municipal system generally have sufficient pressure , but most rural well water systems require boost pumps for a RO unit to work properly .
82 psi is very high for a municipal system . I would guess either the gauge is faulty , or there is either a boost pump on the RO system .

[syncro]

gph vs gpd! Right, thanks.

No boost pump. Gauge has been reading 80 PSI since I installed the unit a few months ago. I only have a small nano reef so I haven't run much water through it. I do run it occasionally for a minute or two with the flush kit bypass open. I haven't measured it other than eyeballing with a 5g bucket so it possible it is outputting 3 gph / 72 gpd.

[mike31154]

My system input pressure is also around 80 psi, give or take. I adjusted the Pressure Reducing Valve (Watts 25AUB) in my plumbing to bump it up from the default/standard 50 psi. According to the spec sheet, the adjustment range is from 25 to 75 psi, so beats me how I'm getting 80 and on occasion even a tad over 90 psi. Maybe it's broken. City water pressure upstream of the PRV is generally around 110 to 120 psi. If you find you have one of these in your plumbing, it more than likely has a strainer which should be checked & cleaned periodically.

I've been thinking about installing a king size whole house sediment filter just upstream of my PRV. This would allow me to remove one of the sediment pre filters from my RODI system & perhaps up the performance.