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Author:
bud (TX)
Built my house 17 years ago and had it set up for continuous hot water by way of a recirculating pump.
Pump is connected to the hot water return line that goes into the bottom drain of my electric 80 gal. water heater.
We don't use our jetted garden tub very often and have noted that when hot water is run into the tub, after a few minutes (maybe a gallon or two of water) that a tan fine consistency grit accumulates in the tub. It looks almost like fine brown sugar.
The original plumber has no idea what the grit is and now won't even return my phone calls.
A second plumber flushed the hot water pipes using a chemical (2 pints?) that is used for tankless water heaters. He said this chemical is required to keep warranty in effect for tankless water heaters.
Well, after flushing we got a dark- not tan- scale looking grit in the tub. I replaced the water heater on May 20-before the flushing- and have since drained it about 4 times getting little grit.
The lavatory sink next to the tub also gets a small amount of the grit when running water in the tub. The shower next door to the tub and all other hot water outlets do not get any grit.
We disconnected the recirculating pump and found that the only way to get hot water in the kitchen sink and elsewhere was to run a stream of water in the tub at the same time. Plus, grit still accumulates in the tub. Go figure!
We also installed a filter in the hot water line coming out the top of the water heater that goes into the house. No grit!
A third plumber has now suggested that the tub water fixture has corroded and is causing the grit. I don't buy into this since we have to run a gallon or two of hot water before the grit appears.
My online research says a continuous recirculating pump can cause this problem and eventually will cause pinhole leaks in the copper pipe. Especially so if the pump has a high velocity.
My Grundfos UP 15-42 SF water velocity is unknown to me and Grundfos technical support says this pump is obsolete and can't provide velocity.
I will really appreciate any help from this forum in resolving this problem.
Edited 2 times.
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Author:
North Carolina Plumber (NC)
Is the filter you installed at the heater rated for hot water ?
What micron is the cartridge ?
Excessive velocity will definitely erode the copper piping.
I would take a sample of the dirty water and have it tested to see exactly what the debris is, then a solution can be determined.
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Author:
hj (AZ)
It could be resin from a water softener, or debris on the bottom of the water heater that is being stirred up and circulated by the pump.
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Author:
dsc3507 (PA)
Couldn't this be rust from the hot water heater tank? If it didn't happen for a year or two in the beginning maybe it oculd be that.
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Author:
bud (TX)
This is the 2nd time a filter has been installed at the top of the water heater where the hot water goes into the house. It's just that nothing ever accumulates in the filter. This leaves me to conclude that the grit is in the copper pipes under the slab. The circulating pump circulates a little of the grit back to the water heater. The water heater was just replaced 6 weeks ago and the same grit comes thru the copper pipes into the tub.
Edited 1 times.
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Author:
Paul48 (CT)
As NC Plumber stated, you need to properly identify what the material is. I'm really suprized that Grundfos was unable to provide you with the pump curve for that circulator, even though it is obsolete.
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