Adding under-sink water heater to tankless home system. There are two hot water supply lines originally each with cutoff: one for dishwasher (at least 3/8"; another for kitchen faucet (1/4". I would like to run both hot water lines through the new heater (in and out) to supply hot water until tankless supply catches up with its own hot water. Is there any problem with using both size lines as input/output for under-sink heater (basically with T connectors/adapters)? Dishwasher and faucet will not be running at same time generally. Should I reduce to one supply with cutoff valve and divide output for both faucet and dishwasher?

so, you want to put a tee on the inlet to attach the existing HW lines to and a tee on the outlet to run to the fixtures?
that set-up will function just fine.

Ok, that's what I thought would have to be done. T's on both input side and output side. Thanks!!



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