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Author:
jberenyi (UT)
I know that getting pinhole leaks has been discussed before but my question is slightly different. I'm mostly interested in knowing how to calculate the fps of my pump. Here are the details:
Grundfos UP 15-18 B7/TLC
0-14.5 gpm
Timer version
3/4 pipe
1/25 HP
Knowing the above how do I calculate the fps for this pump? After 4 years in this new house I have sustained two pinhole leaks in the copper pipe just exiting the output of the pump.
Edited 2 times.
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Author:
hj (AZ)
You do not need to know the FPS, just install a valve on the OUTLET of the pump, then shut it down until the water just stays warm.
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Author:
jberenyi (UT)
I have read about this. It has to be a glove valve.
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Author:
hj (AZ)
A globe valve is better, but they are getting hard to find.
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Author:
jberenyi (UT)
My plumber came out the other day and free of charge he cut the 18" copper extension that went to the PEX tubing. He said the copper was paper thin. He said in the last couple months they have stopped doing the copper extension off the recirc pump due to swirling action inside the copper pipe at about the 2-3" point exiting the output of the pump. He basically ran Pex all the way to the pump and sweated in a barb connector. All is well now.
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Author:
Shooter (Canada)
Hi jberenyi - A Grundfos UP 15-18 B7/TLC is way too large a pump to be using on domestic hot water recirculation. If it is pumping ten gallons per minute the water velocity is over 6 feet per second - which is way too high - that's why your copper pipes are wearing out from the inside. You need to reduce water velocity to less than 2 feet per second.
The copper gets pinhole leaks because of too high a water velocity, but we have also seen cases where the PEX splits because of too high a water velocity. Uponor literature specifically says that where PEX is used in domestic hot water recirculation, water velocity must be less than 2 feet per second.
Suggest you install a much smaller Grundfos UP 10-16 BN5 LC pump which is designed for hot water recirculation and will do only 2 or 3 gallons per minute.
Then install a circuitSolver by ThermOmegaTech. Model CS-1/2-115. That CircuitSolver will only allow the exact amount of flow to keep the recirculation temp at 115º F. A CircuitSolverTM is like a “Silver Bullet” for preventing domestic hot water leaks.
Glad to discuss.
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