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 .