Damage recirculating pump?

[thodges]

I live in a condo building that has one water heater for all 20 units and a recirculating pump to keep the water warm to all units. I didn't know we had a recirc. pump and was going to have some plumbing work done. The plumber wouldn't do the work unless he could verify whether we had one and if so, turn it off before turning off the building's main water. He said that turning off the water without turning off the pump would damage the pump. However, thinking back on previous emergencies other people have had in the building, the water has been shut off in the past, sometimes for several hours, without damaging the pump.

Can turning off the water damage a recirculating pump?

[Bob F]

Running a pump with no water flow can damage the pump.

[RBM]

Yes, if it runs dry. and those bronze pumps aren't cheap

[thodges]

Thanks Bob. Do you know if there's an amount of time it can run without water or if certain kinds of pumps can be damaged more than others? I trust that you and my plumber are telling the truth, I'm just trying to explain why our pump was not damaged when the water has been turned off in the past.

Thanks!

[Don Young]

If the pump drains dry, running it can damage the shaft seal. It is entirely possible to turn the water off hundreds of times without that happening but it is certainly can happen.

Don Young

[RBM]

Thanks Bob. Do you know if there's an amount of time it can run without water or if certain kinds of pumps can be damaged more than others? I trust that you and my plumber are telling the truth, I'm just trying to explain why our pump was not damaged when the water has been turned off in the past.

Thanks!

It may very well have been damaged. It doesn't necessarily show up immediately

[Claude Hopper]

Circulater pumps are water lubricated. Shutting off the water supply won't hurt it, draining the water pipes will.

[dpb]

...

Nope on the first, yep on the second--depends very much on the particular pump design.

Probably because the valve(s) that were shut didn't include the recirc pump inlet/outlet valves and there was adequate recirculation to avoid running it dry for too long.

As somebody else noted, it's running the pump dry that matters and that wouldn't be likely for quite a while even if makeup is off temporarily.

--

[HerHusband]

Yes, running a pump empty can damage a recirculating pump.

However, recirculating pumps generally "recirculate" the same water over and over again. Even if you turn off the incoming water supply, there should still be water recirculating in the hot water lines (unless you turn on a faucet or otherwise drain the pipes). Of course, you may not be able to control whether someone in another unit uses water while you're working.

I'm not familiar with the typical condo plumbing situation, but I would think common sense would dictate a separate shut off for each unit? In other words, you should be able to turn off the hot water feed to your condo, without affecting the hot water recirculating to other units.

But, if you can't isolate your condo from the main supply, and you need to drain the system (to replace the main hot water heater or something), you should definitely turn the recirc pump off first.

Anthony

[Bob F]

Pumps run without flow can get very hot. Which can cause damage.

[ransley]

I turn off my main and leave pump on if a leak is on first or second floor, my pump is in the basement and would be the last thing to drain. I would have to drain the water heater and that would also be ruined for the pump to be ruined and my water heater is about $2000.00 vs 150.00 for a pump. So it depends on pump location, some buildings have them in the middle as additional boosters, they can easily be ruined if leak is below and pipes are drained. As long as it has water in it, its ok, dont forget to oil it if it has ports.