I need to repair the seals of the automated water valve on my Aquastar, on-demand water heater. However, two very difficult to reach stainless steel screws have seized up and I cannot turn them without further stripping the Philips head. The location prevents me from grabbing the head with vise-grips or other pliers.

Can I, over time, apply lubricant to the few exposed threads in the hope that it unlocks the threads? Should I grind down the head into a square that I can fit some socket over? Is there some other way to get this screw out?

I am planning on waiting until the summer to effect these repairs, when hot water isn't so critical!

  • That's a tough situation. In my experience, lube doesn't help. en.wikipedia.org/wiki/Galling
    – isherwood
    Jan 23, 2017 at 21:43
  • You'll want to use the good stuff, like Kroil. Jan 23, 2017 at 22:17
  • Be sure these screws are not Pozidriv. I gotta mention this since I just today learned the difference and now understand why I've had some things go wrong in the past. I am sure I used ordinary Phillips head screwdrivers on Pozidriv. (I have an Aquastar tankless that has been in service for 12 years and I am facing the same maintenance procedure.) Jan 23, 2017 at 23:42

1 Answer 1


First I would hit the screws with a penetrating lubricant like PB Blaster or Kroil. Then I would make sure that I have the absolute best fitting phillips head bit on the end of my screwdriver. Then I would push into the screw driver with all my might while slowly turning counter clockwise, and cross my fingers that it does not strip. And then if they do strip, then you have some options:

  • cut off the head of the screw. I don't know exactly what your situation is, but many times the head of the screw is what is holding the things together, so cutting it off will eliminate the pressure. Once things are taken apart you'll have a threaded rod stuck into whatever it's threaded into, but if enough of it is exposed then you can use a vice grip to get it out.
  • drill out the screw. This would be difficult on something like stainless steel, and you would also ruin the threads of whatever it's screwed into (if it's a nut then no worry).
  • cut the head of the screw into a square or something to get a socket onto it. Will be too hard if it's a small screw
  • blast away the screw with a torch. Something tells me this would be inappropriate for your situation
  • use a screw extractor socket. I have had good luck with these.

If breaking the head off the screw would compound your problem further because you will be unable to get the threaded rod out, then you're biggest priority should be not to break the screw! If this happens, then a machine shop may need to mill it out.

  • PB blaster is good stuff sometimes I have had some luck slightly tightening and then trying to loosen back and forth helps to work the lube in and break up any Gauling.
    – Ed Beal
    Jan 24, 2017 at 20:06

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