Question about Grundfos UP10-16B5/ATLC Comfort Series 1/33 HP Recirculator Pump with Sweat

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Can i run new hot water return line back to hot water system

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Open following link to view how recirculation system looks:

Ordinarily the cold water line is used to complete recirculation loop.
There is no reason why you cannot run separate line back to water heater instead of using cold water line.
The Grundfos system comes with crossover piece that connects hot-and-cold lines at furthest faucet.
Instead of connecting between hot-and-cold line, simply connect hot to your new hot water return line.

When your new line arrives back at water heater, it must connect to cold water inlet so return water is directed to bottom of water heater.
For critical safety concerns, do not remove TP valve to install new water inlet.
Nor is it best to use extra plug on top of tank to install new water inlet, unless you also install dip tube that directs water to bottom of tank.
In the case of tankless water heater, return line must be connected to cold water inlet also.

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Posted on Mar 14, 2011

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Solution to Excessive Cold Water Wait Time With Grundfos Pump

You can install direct return line that cycles hot water directly back through drain valve on water heater, so hot water circulates independently from the cold water line. This system means cold water is available immediately, and also hot water is available immediately, but means installing additional plumbing line, and removing water heater drain valve. Removing plastic drain valve will probably break off and require hammer, big screwdriver, torch, and 7/8" drill to remove broken pieces.
Here is image:

Or use the timer feature instead of thermostat to precisely schedule when hot water will be available, and thereby also schedule when cold water is available.
Here is image:

Sep 27, 2012 | Hardware & Accessories

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I have an instant hotwater system with the futher most bathroom about 45' away. I am looking at adding a recirculating pump on a timer at the furthermost bathroom to get hotwater quickly in the...

Maybe I am not understanding your problem exactly, but if you have the instant hotwater system installed it should be measuring the temperature of the water in the hot water line and if it drops below the set level it should open the hot water side until the temperature is reached. If it was installed correctly it puts the hot water back into the cold water line so it isn't wasted.

Sep 18, 2011 | Grundfos RCP-96 Recirculation Pump for...

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Hot cold water

Question is not 100% clear.
System is not described.
Hot water will come out of cold tap of you have recirculation system.
Without a direct return line, the cold water pipe is filled with hot water.
So hot water is available immediately, but you wait for cold water when recirculation system is on.

If you install a direct return line, then cold water line is not used for recirculation, and cold water is available immediately.
Another possible solution, depending on problem, is to use timer instead of thermostat to control recirculation system. Using the timer means hot water is inside the cold pipe only when the timed operation is running. This will let you have immediate cold water.
Link above has information how to choose timer vrs thermostat.

If cold water never arrives no matter how long you run the hot tap, then check-valve on recirculation system is not working, or you have crossover on single-handled faucet, or both.

Jul 22, 2011 | Grundfos Comfort System Recirculator ...

1 Answer

I need a diagram for an indirect hot water system heated by a solid fuel boiler and an oil boiler

If you are using more than one heat source you will have 1 more pump than the heat source pumps Main pump = SYSTEM pump pumps through the indirect hot water system and back into itself. This is the system loop. The other two boilers tee into this loop upstream of the indirect tank, downstream of the SYSTEM pump. The cold water return to each boiler tees into the system loop next to and upstream of where the hot water for that boiler tees into the system the loop. The oil boiler will have its own pump on its return line from the sytem loop and the solid fuel boiler will have its own pump. When any boiler fires, it turns on its own pump AND the system pump. If you want a drawing email me send a fax number and I'll fax you a drawing.

Jan 15, 2010 | Aquapure AP431 Hot Water System Cartridge

1 Answer

When installing a new radiator i will cut into the flow pipe and fit it, can i then t-off from that flow pipe to another additional radiator and do the same with the return?

In the typical installation of hot water radiators, there is a Monoflow Tee placed in the supply or return line of each radiator. This allows each radiator to be adjusted to desired temperature. This allows flow of hot water to the next without blocking the supply. I suggest you check your system to see if it is Monoflowed prior to cutting in. Google Monoflow systems for a better explaination.

Jan 02, 2010 | Heating & Cooling

1 Answer

I have a hot water circulator when i turn on the cold water hot water comes out for about 30 seconds before the cold water will come out. What could be causing this?

This is could be because the system is set up to use the cold water line as the return to the HWH.

Hot water recirculation systems generally consist of a pump, an integrated electronic controller, and a zone valve. When the activation button is pushed, or when another type of control turns the system on, the pump starts recirculating cooled water that's been sitting in the hot water line and sends it back to the water heater through the cold water line.

If you would like..Google "hot water re-circulation theory" further explains this senario.


Dec 01, 2009 | Rheem 40 Gallon FVR NATGAS Low WATER...

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Hot water is flowing from the water heater into

boiler type? Combi,standard,if your boiler is a combi the non return valve onto your heating line may be defective thus hot water slippng back through cold line best of luck

Oct 27, 2009 | Water Heaters

1 Answer

Takes too long for hot water.

You need a recirculating line. You will have to hire a plumber to run a water line from the farthest fixture or to the fixture you are concerned about on the hot side and return it back to the water heater. this will cause hot water to constantly run throught the hot water line (via the recirculating line) and when you want to draw water from the fixture, you will already have hot water right at the line.
I know this works with standard tank water heaters, but it is a lil trickier with rinnai units(but very possible) if your plumber pleads the 5th and tries to sell you another unit call the Rinnai manufacturerand ask them how.

Jun 12, 2009 | Rinnai Water Heaters

1 Answer

Hot Water Overflow

Do you have an expansion tank tank  in the line leading into water heater? If not what is happening is that the water is no longer allowed to go back into the city supply.  You said that you had turned it off while you left so the water heats up and has no place to go so the preasure/ temperature P/T valve  opens and lets out the excess water from the expanded supply (heater water) that has no where else to go. It used to be that the extra expanded water just backed up into the supply pipe and back into the main. That is no longer possible in most places by the  National Plumbing code.    The answer may be to install the expansion tank into the incoming line. You can see then now at  all hardware stores where water heaters are sold.

Jan 04, 2009 | Rheem 81VP6S/430126 Water Heater

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