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Recirculating pump's impact on locating source of rust in hot water lines.

Recirculating pump's impact on locating source of rust in hot water lines.


  #1  
Old 10-29-13, 03:43 PM
W
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Recirculating pump's impact on locating source of rust in hot water lines.

I have a two story, 30 year-old, five bedroom house. Hot water is distributed throughout the house via a continuously running recirculating pump located next to the gas water heater on the first floor. As the drawing below will show, the recirculating pump actually returns the unused (return hot water) directly into the cold water supply line feeding the water heater. (No backflow prevention noted on cold water line????)

Attachment 20198

We have noted over the past few months the growing presence of dark rust colored water coming from the hot water faucet for a whirlpool tub located in a down stair's bathroom (not used that often). It can take several minutes for the hot water to finally run clear. Other hot water faucets, not used on a daily basis, also show some brownish tint to hot water for shorter periods of time, but not as much. Hot water faucets used daily, offer little or no signs of rust in water. Cold water faucets are not affected.

Draining the water heater did not reveal much more than a few seconds of rust colored water at the start of the drain process. One plumber suspected galvanized pipes were probably used somewhere along the plumbing route, and were now rusting.

My question: Since the recirc pump runs continuously (5-10 GPMs) and is actually plumbed to the cold water supply (meaning its water is discharged at the bottom of the heater tank), is it possible that the continuous circulation action of the water inside the tank, especially at the bottom, is preventing rust deposits from forming at the bottom of the tank; thus actually concealing a potential rust problem in the tank? I suspect that rust deposits are being flushed from the water heater, through the hot water lines, and over time the heavier rust deposits are settling along branches of unused/seldom used faucets depending on their orientation to the main line feeding those faucets.

Any thoughts on the matter would be appreciated.
 

Last edited by wdmcjrd; 10-29-13 at 03:48 PM. Reason: insert attachment
  #2  
Old 10-29-13, 03:59 PM
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If you have untreated water, old steel lined water heater, or steel plumbing there will always be iron someplace in the lines.
 
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Old 10-29-13, 04:05 PM
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Your attachment did not work...

The pump supplys to the bottom of the heater....

Is your concern rusty water????

If only hot side then yes the water heater...and/or pipes

What the yr? make /model?
 
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Old 10-30-13, 08:55 AM
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lawrosa, joecaption1

Thanks for the response. For whatever reason, the "Manage Attachments" button on my screen is no longer responding (telling me to contact the Administrator), so I cannot repost the diagram I initially attached.

The heater is a Rheem (Mod # 21VR75) 75 gal. gas water heater. If the first 4 digits of the serial number are the model month/year, this is Oct - 2001 model. So yes, its is nearing the end of its expected service life.

The return water line via the pump (Grundfos #UP15-29SF) T's into the Cold water intake line, just above the tank. I find that an odd approach, and am surprised not to see a backflow prevention device on the cold water line upstream from the T. Only a gate valves above the T and on both side of the pump.

Yes, my concern is rusty water, but also trying to determine the source. I have only owned the house for four years. With the house being built in the 80's, building codes (Dallas, TX) would not have allowed steel water lines. Since this is a 2-story, slab on grade, that has been extensively remodeled once (six years ago), there is no telling what may be hidden from view.

With a re-circ pump that runs 24/7, tied into the cold water supply. I am suspecting that I am continuously churning the sediment at the bottom of my water heater, and sending it through the pipes only to collect branch lines feeding seldom used faucets. Thus, we find rusty water when we turn on the seldom used faucets, but when we drain the tank, we do not see the expected accumulation of sediment/rust that I have seen from other old houses/water heaters. If the "experts" (collectively speaking) do not believe that is reasonably plausible, then I have other issues like finding the true source, I need to focus on.

Given its age, I realize the water heater should/will need to be replaced soon anyway. However, 75 gallon heaters are expensive to purchase/install (plus modify the recirc plumbing). Additionally, the previous owners, when they remodeled were kind enough to enclose the water heater in a nicely finished closet with a door opening 4" narrower than the diameter of the water heater. So, some deconstruction will have to be coordinated prior to any replacement. The alternative, is to re-pipe the house, and/or attempt to do a limited re-pipe coupled with converting the house to multiple tankless water heaters.

If I am going to have to spend several thousand dollars on replacement or even more given the other options, I just want the assurance that it will resolve the problem.
 
 

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