Leaking Pump

23 Oct 2017
Reaction score
United Kingdom
Good Sunday morning! I noticed that underfloor heating pump is leaking. The heating is working..

I am wondering, for fixing the leaking, do I need to replace the whole pump or change the washers, or just use sealant? Some suggests that just tighten the joint. It is tight and in-movable. Please advise. Thanks.
Last edited:
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1. Where is it leaking from, the joints at one or both ends, or from the centre of the pump?
2. If from the joints, then, in order:
2.1 Try tightening the big nuts securing the pump to the pump isolation valves.
2.2 Change the sealing washers e.g. Screwfix item 4252J
2.2a Isolate the water using the isolation valves either side of the pump body. These are rarely 100% reliable so be ready to re-tighten nuts and have some old towels / shallow trays / bucket handy.
2.2b Loosen the big nut securing the isolation valve to one side of the pump. Allow any residual water to drain. The valve fits with a flat face on the valve against a flat face on the pump, with a sealing washer in between. Force the pump very slightly away from the valve, remove the old washer and fit a new one. Re-tighten the big nut.
2.2c Repeat 2.2bfor the other end of the pump
2.2d Open isolation valves.
3. If from the centre you will need a new pump. Take a note of the make and model of the old one, and get an exact replacement or one which states it is a suitable replacement. Then:
3.1 Isolate the electrical supply to the pump. I'd advise turning any consumer unit(s) off at the main switch.
3.2 Disconnect the electrical supply to the old pump as close to the pump as possible. Usually some form of wiring centre.
3.3 Replace pump as 2.2 above.
3.4 Connect electrical supply to new pump.

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