Water filter swap

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Sep 12, 2018
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I am planning to replace a model year 2015 GE Profile 3-cartridge RO System with a new GXWH04F "whole house" single-cartridge filter under the kitchen counter, and would like to avoid re-plumbing by using the same drinking water faucet and plastic lines already installed.

Our home water pressure is regulated to 55-60 psi, and the cold water inlet for the RO is plumbed with a 1/4" plastic line fed by the PEX equivalent of a 1/2" branch line. The main kitchen faucet connects to the same branch line, and a separate drinking water faucet is connected to the output of the RO system. The line from the RO outlet to the separate drinking water faucet is 3/8" plastic. The inlet and outlet fittings on the GXWH04F are 3/4" plastic NPT female.

Assuming I install the proper push-fit adapters on the GXWH04F housing, would I have any problems supplying this filter with a 1/4" water line at 55-60 psi and using a 3/8" output line to the existing faucet? Can I continue to split the output between the faucet and 1/4" refrigerator water line on the existing push-fit tee? Any special precautions I should follow?

To anticipate some questions, the house has a real whole house filter and softener (Hague 63BAQ), but my problem is the smell and taste from PEX outgassing caused by the chlorine in our city water, and the PEX lines come after the whole house filter.

The RO system has no effect on the PEX outgassing smell and taste, and we're tired of paying $100 a year for new pre and post filters for a system that provides no benefit. My wife would also like to reclaim the giant area under the sink that is currently occupied by the RO tank. It would be inexpensive enough to swap the GXWH04F and carbon filter for the RO system, as long as the existing plastic piping sizes are compatible with my objective.

If I can avoid it, I would prefer not to mess with changing the valve fittings connected to the PEX branch stub, because the 18" PEX cold water stub-out under the sink is unsupported, and I'm not sure how much torque stress the PEX fitting or piping can handle.
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