I'm trying to descale my tankless hot water heater but have run into an issue. When I go to turn the water off, both valves will not turn at all. They have two yellow handles (looks like Apollo brand) and I can't get them to budge. Is there some trick to these valves? Or is this just a sign that the previous owners haven't done this in a while and it's possible both valves are stuck (sigh...)...

  • 5
    Standard ball valve? Probably just stuck. Look closely at the swing stop and make sure you're pushing the right way.
    – isherwood
    Feb 6, 2018 at 16:48
  • My tankless isolation/ flush valves are closed by an aprox 90 deg CCW turn (as seen from the handle side). If you verify the correct direction on yours, you could use a wrench on the handle. Feb 6, 2018 at 20:12

1 Answer 1


Post a picture of the valves to clarify, but in my opinion those valves are blocked by limestone, so you have to replace them.

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