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Plumbing in the Home/tankless water heater problem


hi jay,
my 6 year old bosch tankless water heater sporadically stops heating.
i'll be taking a shower and all of a sudden, after a couple minutes, the water turns cold. i have to turn off then turn back on the hot water to make the hot come back on.
don't know why. any ideas?

Bosch  model 425HN

thanks in advance

I sounds like a flow switch problem. Water must be flowing to function otherwise it would burn out. The switch may be going bad or the copper tube heat exchanger is partially plugged and needs to be delimed. Find your manual for directions or call the installer. Have the switch checked. Replace it it's not repairable. Deliming is a little coplicated and should be done professionally.  

Plumbing in the Home

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Jay Nicholas


Plumbing & Heating (warm air, hot water & steam heat)


40 years in the business, 40 years as a lic. master plumber in NY State. Retired

Graduated Magna cum laude at the School of Hard Knocks

Past/Present Clients
Commercial, residential and light industrial. You name it ...I have probably worked on it

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