Sizing Circulation Pumps The article "Hot Water Circulation" (12/10) left me confused. First, it states that pumps must be correctly sized or pipe corrosion might occur - something I have seen firsthand. But then it goes on to state that when using a tankless water heater, you should go to the largest pump available - hence my confusion. Does the tankless system somehow negate the corrosion problem? Also, is corrosion a problem with PEX piping? Randy Matthews DallasThe reason the tankless heater necessitates a larger pump is that the heat exchanger coil in the unit creates lots of friction....

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