Failing water pump?

[[DHT]Osiris]

I have an in-line water pump (one of many) in a radiant heat system that appears to be nonfunctional. I hear whirring (louder than it should be), it's vibrating/indicating moving parts which varies correctly with the speed dial on it (low/med/high) but it never appears to actually push hot water through the output pipe. Pump gets hot, nothing on the pipes though.

We recently had a pretty catastrophic water breach while we were out of town, so the pump was potentially running dry for a while, several hours at minimum, a day or two at maximum. I know that's super Not Great for those pumps so I won't be surprised to know it's borked, but curious if anyone's seen this and recovered before. Other pumps are fine, I bled the line in case it was air locked (was air in the line), but nada otherwise. My bleed port isn't isolated to that pump so I had water moving from more than that source.

 

[skyking]

I'd still be looking for an airlock.

 

[[DHT]Osiris]

I'd still be looking for an airlock.

How would I suss that out? I had the zone active, pump running, and hooked up a hose to two different drains connected to the system that loop can access, and did actually get some air out of it, but still nothing hot moving past the pump.

 

[skyking]

I'm not there to eyeball it.
I'd pull the pump and test it in a bucket right by where it is wired. My bet is the pump is still OK. You may have to isolate and backflush the run to get it going.

 

[[DHT]Osiris]

I'm not there to eyeball it.
I'd pull the pump and test it in a bucket right by where it is wired. My bet is the pump is still OK. You may have to isolate and backflush the run to get it going.

Annoying, if I was going through the effort of pulling and resoldering I'd use a spare I had from a broken loop 😛 Trying to avoid paying someone to come out here, but plumbing beyond things that screw in is a little over my pay grade.

 

[skyking]

Ok. Don't solder it back in. Figure out how to install a union on both sides of that pump if at all possible.

 

[deadlyapp]

Agree with skyking. My entire professional life is around pumps and it just sounds like it's not properly primed.

You might have blown it out from running it dry but for the most part they are built with pretty rough clearances so it may be fine.

Get water to it by trying to run water on the suction side and venting from somewhere far downstream from the pump.

If you don't have proper fill/vent spaces, this is a good time to add them

 

[[DHT]Osiris]

So I isolated everything from the pump to a hose line, and the pump had access only to water from our boiler loop, and eventually the flow slows to a drip while the pump is running. It's possible there's a blockage I guess but I find that very unlikely. I did successfully bleed air from my other two loops though so that was good to do.

 

[deadlyapp]

Could be slowly deadheading itself if something is causing a blockage down the line and the backpressure gets high enough, or could be starving itself if suction line has a similar blockage.

Unfortunately only way to really tell is to pull it out at this point

 

[[DHT]Osiris]

One other question, something I'm seeing on my setup that I'm not seeing in online diagrams that I've always been curious about... there's a connector from my domestic cold, specifically to the radiant heat supply. Everything I've seen (and logic) dictates that there should only be a post-furnace realm. It does have a shutoff valve that's been open since I moved in (so previous residents had it open). Anyone seen this?
Very roughly, something like this:

 

[waffleironhead]

My guess is that line is for adding more water to the system, but its usually tied to a pressure regulator and one way valve. Commonly called a "make up valve"
If its just directly tied into the boiler system, that would be no bueno and I would shut that valve. Especially if there is antifreeze in the boiler loops.

 

[[DHT]Osiris]

My guess is that line is for adding more water to the system, but its usually tied to a pressure regulator and one way valve. Commonly called a "make up valve"
If its just directly tied into the boiler system, that would be no bueno and I would shut that valve. Especially if there is antifreeze in the boiler loops.

No antifreeze, and I suspect you're right. No one-way valve or pressure regulator though, just feeds into the 'intake' section of the radiant heat, separate from the actual 'intake' of the boiler (though it'd eventually loop back through it).

As an aside, I confirmed that when that valve is opened, water makes its way through the nonfunctional loop (and cold water comes out of the drain). When the cold is shut off, eventually the water trickles to a stop, which tells me the pump isn't 'pushing' correctly, and any water movement through the system when the pump is on is purely based on pressure from our cold side tank. My plan at this point is to pull the pump, swap it with one right next to it that's on a defunct line, swap the wiring, and see if I'm correct in my assessment.

 

[[DHT]Osiris]

Update, now that it's getting cold enough for me to care. I was right. Pump failed from overheat/overpressure. Swapped with known functional in a disused line, worked immediately. Plumbing guy thanked me for doing all the hard work for him.