The valve nuts holding my central heating pump have locked solid, probably held by plumbers' paste (Boss White). Iv'e tried extra leverage but to no avail. The gate valve is 28mm. Any good ideas on how to free up the nuts to replace the pump?

Sam, May 2009

Hi again Sam
My body building, weight lifting, plumber Son did his best and assured me that I did mine too. He is sure that the plumber that fitted the pump with the new boiler has used either Hermatite or Paste. He assures me that the nuts usually come off relatively easily and that mine is the worst that he has come across.
My worst fears have been realised, and the only ansewer is to drain the system, cut the pipes and fit new isolating valves on either side. Totally defeating the purpose of using them in the first place.
A new problem re draining the system has come up, as the guy who fitted the new boiler removed the system drain cock and didnt put a new one anywhere in the new system.
Has anyone anywhere got any suggestions as I shant be tackling the job for a month or two due to holidays. The telephone number of 'Watchdog' might help too, though the plumber is almost certainly dead by now! either of old age or murdered by a dissatisfied customer.
How on earth do I put in a drain cock without releasing 30 gallons of water into the house?
Thanks a lot in anticipation.

Colin, July 2009

Sorry I dont have the answer - yet. I am working on a similar problem today -Saturday 18th July 2009. My pump is an SMC but the problem is the same. My son is a plumber and is on his way over as I type.
I soaked the joints in vinegar every day for a week. and wire brushed any outside scale. this morning I heated the outside nut with a fine flame from a blowlamp expecting the nut to expand relative to the valve body. I am using the proper pliers for the job and have rigged up an extension to get more torque, and so far - NO LUCK! When I originally fitted the pump 20 years ago, I thought that by fitting an isolating valve on either side of the pump I would not have to drain the whole system, and to change the pump would be a 5 minute job!! The isolating screws have freed up fine and the water is no longer circulating. I have a horrible feeling that the only way I am going to succeed is to cut the darn thing off and drain the system and modify the pipework. I'll keep you posted !!!! Ive given up until my son arrives.

Colin, July 2009