Help, rust blob! From recirculation pump?

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Old 05-19-14, 05:58 PM
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Help, rust blob! From recirculation pump?

Help, rust blob! From recirculation pump?

Ever since I changed my hot water recirculation pump to the one shown in this picture, I get rust in my water. Is there anything I did wrong here? Is there a dielectric problem?

NEW PUMP:


This new pump is made of steel but thought I was dielectrically ok since, as you can see in the photo, the transition is from the steel pump to the brass flanges, then to copper. Besides, the pump does not even touch the brass, there are rubber O-Rings in between. The bolts, as you can see are galvanized, but Iím not sure if that matters.

Where and how do I see the rust: When Iím gone from the house for 3-4 days and thus turn both the water heater and recirculation pump off (Iím on propane which is more expensive), when I return, if I turn a hot water faucet on (before restarting the recirculation pump) then after about one gallon of water, this intensely rusty water comes out for a few seconds. BUT, if I restart the recirculation pump first and then open the faucet then I get no rust (I assume in this case the pump dilutes the rust into the entire hot water network and Iím thus no longer able to see it come out as one concentrated blob).

Why do I suspect the recirculation pump:
Aside from the fact that seeing the rust depends on whether I turn the recirculation pump on or not, I also did not have the rust issue with the older pump I replaced (it broke). Here is the photo of the old pump. So it must be the new pump causing the rust. I believe the old pump was brass, while the new one is steel, but I donít think all this rust is normal. Something in there is rusting at a very fast rate and that does not seem like a good thing.

OLD PUMP:
 
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Old 05-19-14, 06:39 PM
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Domestic (potable) water has tons of dissolved oxygen in it, you MUST use a bronze or stainless steel pump in your recirculating system.
 
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Old 05-19-14, 09:24 PM
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The steel bolts touch the brass. It's just a thought. I don't know if it matters. Obviously, you already know about problems with dissimilar metals.
 
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Old 05-19-14, 11:09 PM
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The steel impeller of the pump is sitting in an oxygen rich water environment. It is the impeller that is rusting with an assist from the iron pump body. Any corrosion due to the flange bolts would be at the bolts, not internally.
 
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Old 05-20-14, 11:35 AM
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Thanks for the info Furd. I guess I installed the wrong pump for this application. Should have researched it more. Pity because it was the only pump I could find that was an exact fit for my old Bell & Gossett SLC-25 in the second photo. I was trying to avoid any re-plumbing. I had done a google search on the SLC-25 and this steel NRF-22 was the only replacement that came up.

Perhaps someone can help me with two related questions:

A. Is there a way to discover which other pumps (bronze or stainless this time, of course) may fit in the existing space and flanges? Is this a common enough, or perhaps standardized setup that I may be able to find a replacement? It seems odd to me that a pump change would result in replumbing most of the time.

B. Would I be causing myself more problems by leaving this pump in while it lasts (I assume it will not last long at this rate). Is there some detriment to the rest of the plumbing from the rust injected into the system? I donít see rust particles (at least not yet).
 
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Old 05-21-14, 01:35 AM
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Lots of different pumps will probably fit. Two other manufacturers are Taco and Grundfos. Any decent description will note the flange-to-flange distance of the pump. Further, you have lots of room to the right of the pump to modify the piping if necessary. The "duty" of that pump is really minimal as all it is doing is moving the water throughout the return piping.

Just remember an all-bronze pump or a bronze pump with stainless steel wetted parts. Bad side is that it will cost considerably more than that cast iron pump.

And no, no real disaster other than the pump will likely fail in a fairly short time period, maybe a year, give or take.
 
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