UV usage reader question for Professor POU/POE

Sept. 30, 2013

Question about a POU treatment that consists of a one gpm UV (ultraviolet) unit, which feeds a five-stage RO system with a booster pump and a 40 psi pressure tank.

Hello Professor,

We have a well water customer in Alberta, Canada whose water we can’t treat to their satisfaction. I have attached three lab reports. One is the raw well water and includes total coliforms and fecal coliforms. One sample is the water after the POE (point-of-entry) treatment and does not include the bacteria tests. Another analysis is the final RO (reverse osmosis) product water and does include the total and fecal coliforms.

The POE treatment consists of a fine-mesh resin water softener to soften and remove traces of iron, a 20-micron sediment filter and a 1.25 cubic foot mixed bed of GAC and catalytic carbon for color and odor removal.

The POU (point-of-use) treatment consists of a one gpm UV (ultraviolet) unit, which feeds a five-stage RO system with a booster pump and a 40 psi pressure tank. Final polishing of the water leading to the faucet is a mixed bed DI (deionizer) cartridge. This was added as a last-resort “catch all” when the RO water didn’t seem good enough.

The house has a submersible pump and pressure system that runs between 30-50 psi and puts out over eight gpm for backwashing the filters. My client complains of a “lemony” taste in the water from a detergent-free clean water bottle.

The well has been shocked. All internal components of the RO system, as well as the storage tank, have been thoroughly cleaned and ultimately replaced. They appear normal and the laboratory results seem to verify it. The taste is definitely impacted by whatever this contaminant is. I have verified it myself including conformation of the absence of detergent residue.

I can see by the coliform numbers that we should be considering a whole-home UV system, but it appears unlikely that this is the immediate problem.

Read the Professor's complete answer here.

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