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Bosch Combi 151 Very low hot water flow at all faucets

jslone80 Member Posts: 4
I recently purchased a home with a wall mounted Bosch 151 that was installed in Dec. 2016. My system is on a well. The cold water comes out of the faucet with great pressure but when you switch to using the hot water the flow drastically decreases. i would say by more than half.

Any thoughts on what could be causing my issues?


  • Is this hot water flow problem only at one faucet or all of them?
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • hot_rod
    hot_rod Member Posts: 21,898
    Could be a strainer on the cold supply somewhere. The manual would show the location and cleaning instructions.

    Or the HX could be liming up and require a acid flush. There are kits available to flush them with a pump and cleaner in a plastic bucket.m
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Jamie Hall
    Jamie Hall Member Posts: 22,972
    Or is there a mixing valve somewhere which is stuck?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Tom_133
    Tom_133 Member Posts: 880
    There is a brass tee that is shipped with the unit that would be installed on the domestic side. As hot rod mentioned thats the best place to start. Shut off water at well, drain off pressure, and remove nut on the wye strainer, there is a tube in there you can pull out and clean.
    Montpelier Vt