I want to replace the washer inside a boiler drain valve because it's leaking. However, I am unable to unscrew a nut that holds the valve stem in place. I have tried a variety of hand tools, so far it hasn't budge. Do you think an impact wrench would help in this case, will it damage the pipes and/or other connections of the system? In general, is it good practice to use impact wrench on plumbing work?

The red arrows points at the "nut" (not sure what to call it) I want to loosen. The valve is a hammond 710. enter image description here

Thanks in advance.

  • I think the nut to the right of the arrow is the one you want to loosen to get at the valve stem. You'll want to place a second wrench on the nut with the arrow to provide counter-force so you don't damage the plumbing in the boiler.
    – HoneyDo
    Nov 23 '21 at 4:26
  • I was able to get that nut unscrewed, but that's not the nut to get the stem out, unfortunately.
    – user61228
    Nov 23 '21 at 4:32
  • Just replace the complete valve, if the seat is damaged then even with a new seal it can still leak.
    – Solar Mike
    Nov 23 '21 at 6:41
  • For plumbing you use two wrenches. If the first two don't work, you get bigger wrenches. If they don't work, you add big pipes to the wrenches. Penetrating oil might help also.
    – crip659
    Nov 23 '21 at 14:13
  • 1
    For using impact wrench, it sounds like a good idea(hold my beer type), but plumbing nuts and pipes are made with softer metals and most times will probably be ruined/rounded, and maybe twisted off.
    – crip659
    Nov 23 '21 at 18:08

It may be, judging by your red arrow, that you are trying to turn the wrong thing.

Do not use an impact wrench. Use two pipe wrenches. It looks like the drain is out at the end of an "arm" of pipe, and if you turn too hard with one wrench or an impact wrench you'll likely damage the area marked as E below.

To repack the stem you want to hold A steady while turning B as shown. To remove and replace the drain you want to hold C steady while turning D as shown.

enter image description here

To answer your other question, "in general" brass plumbing parts are weaker than their old seized up screw connections. By using too much force to free up a seized part, you may damage random things in unpredictable ways that may be hard or impossible to fix. In general you should make increasingly aggressive attempts to free up the desired connection but you do so purposefully, and at some point you give up and intentionally remove or cut or grind off a larger section of work, in a way that includes a plan to replace it.


I would use heat, your seat is already leaking so a torch would be a better option. Heat applied to the left of the arrow. Depending on the type of valve stem packing you will probably need to replace that also but since you are rebuilding the valve it would be a good idea to re pack it anyway.

  • Thanks for the suggestion, tried that but still couldn't get it out.
    – user61228
    Nov 23 '21 at 17:43
  • Most of these are anti clockwise or counter clockwise but I have found a few that unscrewed in a clockwise rotation. I know almost everything is normally “right hand threads” except hazardous gasses, but I have found some valve bodies that were left hand threaded, might be worth a try , older valves in some cases are better quality.
    – Ed Beal
    Nov 23 '21 at 20:23
  • Thanks for the tip, will keep that in mind, haven't tried turning it clockwise, too late now, just replaced the whole valve.
    – user61228
    Nov 24 '21 at 15:54

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