Recirc pump repair

[m100psi]

Hi,

The recirc pump that was installed in the house when I bought it is no longer working. I contacted Grundfos and they said one service part is available, a replacement cartridge kit. I assume it's accessible by removing the screws in the photo? What is the best way to diagnose whether replacing this will fix the pump?

Thanks very much,
Matt

 

[Gary Swart]

Have you compared the price of a new pump against the cost of this repair part which may or may not fix the problem?

 

[Sponsor]

 

[Jadnashua]

I'm not familiar with that pump, but often, the cartridges cost nearly as much as a whole pump. But, if you're trying to save the cost of a plumber, in theory, unless the pump's body is defective, the replacement cartridge contains all of the electrical and wear parts, and, you may be able to do it yourself easier than an R&R (remove and replace) of the whole thing.

 

[Gary Swart]

I must take exception to Jim's remark about just replacing the innards being easier that replacing the entire unit. At least my Laing pump would not require a great deal of time or effort to replace. A couple of cuts, a couple of fittings, and a couple of sweat joints. Anyway, do check the prices for the repair part against the new pump.

 

[m100psi]

Thanks for the responses. Changing the whole pump is an option, though I'd prefer to avoid it if possible--there are valves and unions on both sides. I'm no plumber, but I can (unattractively) sweat what I need to. New vs. repair part is about $200 (assuming the timer module is reusable) vs. $85. I figured if knowledgeable folks said the replacement cartridge kit generally fixed bad pumps, I'd prefer to save the cost and labor of installing a new one.

Thanks,
Matt

 

[Gary Swart]

That's a pretty big difference alright. But, if there is a union in the line replacement should be pretty simple. No cutting or sweating necessary, just uncouple the union and disassemble from there. Guess this doesn't answer your question, but you have a tad more info that your started with.

 

[Jadnashua]

All pumps are not created equal...some are easier to swap the cartridge than others. A plumber is likely to replace the pump since, if there is some issue with the housing, the cartridge may not fix it, and then it's more work...hard to warranty things. He'd get blamed, regardless of what failed. If time is not an issue, such as may be a factor with a DIY'er, unless something was leaking or obviously bad with the housing that the cartridge didn't replace, I'd probably consider the cartridge if it is significantly less. This is probably the case on a bronze or SS pump, probably not that big of a difference on say a heating circuit since those parts can be quite a bit less expensive. Potable water would quickly eat up a pump designed for hydronic, which is why they need to be SS or bronze.

 

[m100psi]

Thought I'd follow up on this having resolved it, though I'm not sure how useful it will be to anyone since I don't know why it's resolved. I took the pump apart to have a look at the cartridge and see if I could see anything obviously wrong with it. I plugged in the open pump and the little jerk started spinning like it had been doing it the whole time (which I know it had NOT been, now that I hear what it sounds like and feel the vibration). Guess it just got stuck or something. I cleaned out the calcium best I could, put it back together, and it seems to be working fine.

One follow-up question: some faucets much farther away from the the heater seem to get hot (now the pump is fixed) faster than others close by. Is this because there are parallel paths hot water takes to the various access points, and the pump only exercises one of the paths?

Thanks,
Matt

 

[Jadnashua]

FWIW, those pumps are lubricated by the water moving through, so running them dry is to be avoided. A short stint probably didn't do anything, but a longer one would likely ruin the bearings. Those motors are quite small in Hp, often in the 1/30th Hp range, so something binding it could cause it to stop operating. IOW, they do not have enough oomph to start if there's something holding them back - they need to be able to move freely.

Water flows through the path of least resistance. If there are multiple paths, that could be part of it. But, the more likely thing is there may only be one cross-over, and everything else branches off of the main line. If those branches are different lengths (likely), then it will take more time to purge the cooled off water from them to get the hot that is in the main line. If you have crossovers for all branches, something's going on in that branch.

The unit I have installed only has one crossover at the furthest point from the WH. The two bathrooms both get hot almost immediately, but the kitchen is about 10' from the main hot water supply line, and takes a bit more time to get hot. It's still much better than before the recirc system.