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Can I install an on-demand hot water heater with a hard water source?

gcdesc | Posted in Energy Efficiency and Durability on

Our home in mid-state Vermont has an old furnace that heats our water. We want to replace the furnace and I heard that an on-demand hot water heater might be a good approach in a new system. However, we have a bit of a hard water problem and I’ve also heard that hard water and on-demand systems don’t mix. Is there a solution to this problem?

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    You are right to be concerned about hard water and DHW. The problem is that it's difficult to say how hard the water needs to be to create the problem. If it's just leaving rings in the toilets and build up on the shower walls and you are living with it without "needing" a water softener then it's likely no big deal.

    I just install a ball valve and boiler drain at the cold water input and a ball valve at the hot out so I can run a gallon of vinegar through it from time to time by pumping it out of a bucket using a sump pump and a washing machine hose and back into the bucket out of the PT valve. let it run for a few minutes, rest for a few and run again and you are done, no big deal. The good modulating water heaters (Rinnai, Tagaki, Pronto, etc.) should have an error code that pops up on the controller to let you know when to rinse out the system.

    There were some cool new condensing instant water heaters at the International Builders Show in Las Vegas last month. the Navien was especially interesting. Has a small tank in it that stays warm so as to avoid the "cold water sandwich" phenomenon. Plumbing Guru Gary Klein was saying very nice things about it and I checked out the website when I got home and am planning to give it a shot in one of the houses we are building.

  2. jfincherok | | #2

    I'm specifying Navien in all our homes. I feel it's the best system. They claim that their stainless heat exchangers are more resistant to mineralization than their competitor's copper heat exchangers. I've just begun using these, so I'm far from being an expert. You'll probably be fine if you flush the system more often. (if necessary).

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