Tankless water heater for space heating
I enjoyed reading Mark Eatherton’s response about tankless water heaters. Can I heat all or even part of my house with one of these tankless water heaters?
Isaac Pap, New Haven, CT
Mark Eatherton, a plumbing and heating contractor in Denver, Colorado, responds: It is not recommended that a tankless potable water heater be used for space heating unless it is dedicated strictly to space heating and not also used to heat water for domestic use. The first and most important reason for not combining uses is that during the summer months when the heating system is off, the water lying in the heating pipes can become pretty nasty. The dormant pipes make an excellent breeding ground for harmful bacterial cultures. Water trapped in the heating pipes can contaminate domestic hot water when the heat is turned back on.
Second, the continuous induction of freshly oxygenated water, as happens in any domestic hot-water system, can rust the cast iron and other ferrous components of a heating system prematurely. Last but not least, some jurisdictions may regulate the use of a potable water heater as a sole dedicated space-heating appliance, so it’s best to check with the local code authorities.