Trouble removing CH pump

[IainH]

Running into difficulties removing a CH pump. Have attempted removal by closing isolator valves and undoing union nuts with wrenches (one man on each wrench) with no success, also attempted lubricating oil on union nuts but they appear to be seized.
Planning on using a heat gun on union nuts to help removal, any other thoughts?

Fallback is to remove pump AND isolator values and replace both, but wanted to avoid draining CH system if possible. If I need to do this, can someone give a rough estimate of how long this could take (large 2 storey house, approx 5 rads upstairs, 9 rads downstairs).

Thanks in advance,

Iain

 

[oilman]

An hour to drain it and up to a day to refill and bleed it.

 

[kevplumb]

try partially sawing nuts then split with chisel make sure pump is supported
you will need new nuts which come with new valves they slip off

will if succesfull save a drain down
good luck

 

[Bas]

Don't assume the old valves will work - often they still let a little water through even when fully closed sop you might well have to drain the system anyway.

 

[ali68]

If you hold a heavy hammer on one of the flats and hit the opposite flat a few times with another hammer this has the effect of distorting the nut slightly and releasing the grip on the threads, do all 6 flats.

Works well on steel union couplings etc, your pipework may need to be reasonably supported to allow this procedure with 22mm though.

 

[croydoncorgi]

If you're resorting to splitting the main water pump nuts (which will DEFINITELY get them loose!) you've effectively written off the isolating valves anyway. Even if you could get spare nuts off some new isolators, there's significant risk of damage to the flanges on the existing bodies anyway.

Sounds also like the pump is a write-off (you said you were going to heat up the joints!). In the end you might as well drain the whole system and get some benefits such as removing some sludge, being able to clean out the F&E tank, replace any dodgy rad valves, etc., all at the same time. Once empty, getting the isolators and pump off in one piece should be OK - but do be careful NOT to strain any connections on a copper cylinder - the metal is thin and weak.

SHOULD only take a couple of hours to refill and bleed the system, if the piping is halfway decently designed.

 

[oilman]

SHOULD only take a couple of hours to refill and bleed the system......

Ha!

 

[namsag]

Dependent on position of pump support it and use a small cold chisel to hammer nuts loose a good few shrp hits should free them don`t undo the first one untill you have freed both(don`t attempt if too close to cylinder as you may damage this ) .Nuts can quite easily be cut off without damaging the valves if care is taken. Also if your pump is a 3 speed grunfoss you can just change the pump head and leave the body in position.

 

[croydoncorgi]

Original poster never said WHY pump had to come out.

Also, removing pump head leaving body in place is not 100 percent effective. About 10 percent of the time, the pump 'splits' in the wrong place, the coil and housing comes off but the impeller and water-containing 'can' gets left behind firmly wedged in the body casting. Then you HAVE to replace the whole thing, however awkward!

 

[namsag]

And why would the whole pump have to be changed if the "water can" is left in place a couple of sharp taps and this will also come out of pump housing.

 

[ChrisR]

Cut or file a little groove in the pump nutand use it as a keyway for something like a square ended chisel. Whack it in the direction of undoing the nut. They either undo or split!
There's a big contact area on the face of the pump valve so nicking the thread won't matter - as long as the nut turns on it.

Usually a pump isn't at the bottom of a system so you may need only a partial drain-down when you find the valves don't work.

 

[IainH]

Thanks for all the advice.

In the end, when I went back to look at the original pump and it's replacement, I discovered the replacement is about 6cm shorter. Didn't feel there was enough give in the pipes to make the shortfall so decided to drain the system anyway. After that just removed pump and isolator valves, planning on finishing job tonight.

Again, thanks for all the help!

 

[ChrisR]

You can buy extension bits which make up the gap, by the way.

 

[croydoncorgi]

And why would the whole pump have to be changed if the "water can" is left in place a couple of sharp taps and this will also come out of pump housing

I would suggest 'may come out' rather than 'will'. In many real-life installations, it's just not possible to apply enough force safely to get the can, impeller, etc. out of the base casting. And if you have to remove the base to work on it, why not replace the whole thing anyway. You can only buy complete new pumps from most outlets and if you DO find a replacement head it will probably not be made by Grundfos!

 

[croydoncorgi]

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