What can happen when the wrong pump is installed

[Stigster]

I've just found a load of old photos I took when I was an apprentice. Among them was this standard circulating pump that was installed on an unvented secondary return circuit. It should have been a bronze pump as I'm sure you know. I was called to re-install the unvented cylinder which was up in the loft. It didn't comply in many ways and the insurers picked up on the faults and I was sent to reinstall it to regulations.

When this pump failed the homeowners were away for several days with this pouring mains water from a 22mm feed from the loft into the house. It was a beautiful old place owned by a wealthy elderly couple and the damage was extensive as you can imagine. Much high quality antique furniture was ruined.

Anyway, I thought you guys might like to see a what a pump looks like after being used for the wrong purpose. I believe it took about 2 years to get to this condition and failure.

 

[Keentolearn]

Is this because of hardness/scale, or just because potable water has no inhibitor?

 

[ShaunCorbs]

Is this because of hardness/scale, or just because potable water has no inhibitor?

Was on water mains, body is steel so rusted

 

[Stigster]

Is this because of hardness/scale, or just because potable water has no inhibitor?

On a secondary return the water is frequently replenished bringing new oxygen into the system. The pump oxidises (rusts) and looses its integrity. Then the front fell off!

 

[oz-plumber]

As far as I an tell, that is a brass pump and fit for the purpose it was installed for.

The bodies of the pump are always steel or aluminium and the head of the pump is brass.
I don't think the wrong type of pump was installed.
Something else has gone wrong for the bottom of the pump to be that corroded.

 

[Last Plumber]

As @oz-plumber said, it does look like the right pump. I suspect the seal between the bronze section and the winding case was compromised and that lead to its demise. It probably seized long before the front fell off.

 

[Stigster]

I see you guys are correct. I was a 2nd year apprentice at that time and that's what I was told back then, wrong pump. However I looked up the model just now an it is a bronze pump indeed. I now think Last has the right idea. Either way it is quite incredible just how corroded it became before finally having the front fall off. Don't worry though guys, I towed it beyond the environment.

 

[Last Plumber]

Either way it is quite incredible just how corroded it became before finally having the front fall off.

More than likely electrolytic/galvanic corrosion. Incompatible metals - been a while so can't remember without looking reactivity series up - Aluminium case? carbon steel core, copper winding, bronze body (alloy) etc. once they are linked by water with the right ingredients, pH value etc etc, then away you go.

 

[Chuck]

Anyway, I thought you guys might like to see a what a pump looks like after being used for the wrong purpose. I believe it took about 2 years to get to this condition and failure.

For a failure like that, I'd want to get the water supply tested for pH (should be in range 4 to 8.5), chloride and metal ions. I guess it could be just a simple leak that's got out of hand, but the appearance of the corrosion makes me suspect a chemical or electrolytic cause.

Perhaps a small leak in an unlucky position made a wet link between the copper pipe and aluminium casing, perhaps?

Nice example of why periodic visual inspections are a good idea.

 

[Stigster]

For a failure like that, I'd want to get the water supply tested for pH (should be in range 4 to 8.5), chloride and metal ions. I guess it could be just a simple leak that's got out of hand, but the appearance of the corrosion makes me suspect a chemical or electrolytic cause.

Unfortunately this happened circa 2009 if I remember correctly. I wonder how they've got on in the subsequent years? They were understandably worried about anything else leaking after all the damage was repaired. They had leak sensors installed all over the place and asked me to bring the mains up outside the property inside a cabinet with a big lever valve before taking it into the property. They wanted to turn the supply off every time they left the house after that flood! They also wanted to keep it simple rather than use any kind of remote switching to turn the water off. I bet they still throw the lever every time they go out and probably before bed too.

 

[EvilDrPorkChop]

This is why I tell all my customers to turn your water off whilst you're away on holiday - some look at me like i'm an idiot. Only needs something like this to happen or something even simpler like a flexi or washing machine hose to go to cause a mess.