Water pump issue only after being on holidays

sk8board

Hi
I have a grundfos copper pump for the whole house, bar rads

After any length of time away with work/holidays etc, 1-2 weeks, the pump won't start, makes a strained noise and begins to overheat.
It sounds like an airlock, however I can turn on all hot and cold taps and the water flows freely everywhere in the house, not even a splutter. That water is flowing through the pump no problem.
After shaking the pump a little (as carefully as I can), it eventually kicks into life and will work perfectly, until the house is empty again for a week or so, which could be months.

Any ideas what's causing this? This has happened every time (3-4 times ) since the pump was installed 9 months ago

Thanks

Here's a pic of the system:

esox28

Hey, to state the obvious your pumps impellers are ceaseing, could be from hard water even small amounts of lime is causing the issue.

I have found a no. Of them monsoon pump sticking after prolonged periods of inactivity. Really not much you can do, only one thing I found helped was applying some 3in1 oil to the stainless steel drive shaft between the motor housing and the brass impeller housing while the motor is running.

sk8board

I hadn't thought of hard water, thanks a lot for the answer

My neighbour just mentioned a month or so ago that they were getting someone in to flush their entire system, I must go find out more.

Froststop

sk8board wrote: »

I hadn't thought of hard water, thanks a lot for the answer

My neighbour just mentioned a month or so ago that they were getting someone in to flush their entire system, I must go find out more.

I think they may be flushing the rads, hard water shouldn't be a problem if your on a council mains supply. It looks like a GRUNDFOS WATERMILL

Your main problem IMO is what looks like a Warix Flange on the hot water supply off the top of the cylinder has no vent. You have a high point feeding the hot side of the pump. If it air locks, the hot side of the pump it not moving water until it moves the air out to the taps/shower, thus it will make noise and get hot/sound rough. You may also have a sticking non-return if they are fitted which could add to the problem, which I think they are in the brass connection outlets on the pump.

You say the pump won't start but makes noise, I would think if it's making noise it is running.

It looks like a warix flange and should have an air vent:
http://www.bathroomexpress.co.uk/images/techflow_qt_install_warix_flange.gif

A surrey flange which I think is a better design as no vent is needed:
http://www.silversaints.com/media/50871/shower_pump_diagram_3_500x329.jpg

Johnny777

I have exactly the same pump and exactly the same problem, but I have the cause and a solution.
My pump is 2 years old and if its not used for 2 weeks, it fails to start, but make s a very faint buzzing noise.
To get it to work again, i used to try a few times, power no/power off and then leave it a few hourse and repeat and it would then go.

Well a short time ago I was away for 10 weeks and of course it would not start
Tried the old trick but after 4 days still no joy.
Phoned grundfos watermill who suggested a larger fuse and one minute of as rapid as possible on/off of power.
Tried that without much hope and you guessed, no success. They said it was caused by flouride!

So with nothing to loose took the pump out and undid the four screws on one end, then a small tap and the brass pump came apart - its joined together at its pont of largest diameter and is sealed there with a large o ring.
Well with the outer half off I could grip the impeller and it turned easily, so I put that half back together and took the other ends half off and lo and behold this time I could not turn the impeller at all.
BUT as soon as I slackened off the 4 screws on the first end then I could turn the impeller easily.
So what I found was that the central third of the impeller is a smooth surface that when the screws are tight is in contact with the matching surface of the outer half of the pump which i removed in the first step.
Both surfaces were rough and contaminated with some build up of scum/limescale.
I cleaned both surfaces up with emery paper and finally brasso, cleaned it all up and applied a dab of grease and then with the first end fully tightened up I could then turn the impeller at the other end.
Put it all back together and its like new.
As long as its used every week or so then the spinning cleans the 2 surfaces of buildup.
It's just a pain that you have to do this.

Tips:
With all 4 screwws removed the inner half of the brass pump can rotate and you could assemeble with it in the wrong quadrant (the blocked off section should be at the top). To stop this, put a mark on the inner half of the pump and a corresponding mark on the main aluminium of the motor body. Thay way you will get thing assembled correctly.

Do not swap the two outer end over. Mark them to show which is which.

Its the hot end of the pump which suffers from this build up more than the cold end.

I found on putting it back into service that one of the pushfit connectors was leaking
only a little. I had not undone them when I took the pump and hoses out as one unit. But it seems there was some build up on the pipe ends inside the fittings which led to a poor seal. Cleaning the pipe end fixed it. So maybe be best to clean all these 4 pipe ends.

Good luck with it. Whole thing only took me a couple of hours.

Johnny777

A further quick thought.
Looking at the photo you have the hot end of the pump facing outwards, luckily!

What you could do is to slacken off the 4 screws at the hot end say 1 turn only and then tap the outer part of the brass housing lightly to loosen it. This should be sufficient to allow the pump to turn, let it run for a few seconds then tighten up the screws again, with it still running. Clearly if it stops then just back that screww off a bit.
There may be a little leak from around the peripherary of the brass pump but probably no ,ore than if you took the pump out.

Hopefully after it has run for a bit all the crud will have been scrapped off the two surfaces.