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Comfort Series Hot Water Systems from Grundfos


Tired of waiting for the water to heat up? These innovative comfort systems are especially designed for those fixtures that do not have a return line to the hot water source. For additional information on the use of these great systems, please refer to the FAQ's below.

The Grundfos Comfort Series instant hot water system eliminates cold water runoff at the faucet, using a bypass valve & pump with timer to control water flow to connect the hot/cold water pipe on the farthest fixture.

UP15-10S Instant Hot Water System
Grundfos Comfort Series - UP15-10S
  • No return line required
  • Unique wet rotor design
  • Conserves water and energy
  • Whisper quiet operation
  • Built-in timer & 10' power cord
  • Maintenance free
  • Comes complete with pump, valve, and fittings
  • View diagram
Bronze Body, 3/4" Union
P15-10SU7P/TLC 3/4" union x 3/4" NPT, 115v w/timer, line cord & 1 comfort valve $282.12
Comfort valve only 1 comfort valve $62.82

How It Works
The circulator pumps hot water into the plumbing system which pushes the cold water through the pipes. This cold water then crosses over from the hot piping to the cold piping at the bypass valve. The cold water then runs back through the piping to the water heater. The valve starts closing at 93°F and is fully closed at 103°F. Hot water is then available at fixtures.

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Please note: all brands of instant hot water recirculation systems that do not require a hot water return line can be dangerous. They use a mechanical thermostat, which tells the system when to stop pumping the hot water into the cold water line. This thermostat can, and will, eventually fail - this failure may cause hot water to be pumped into the cold water line. This hot water can cause mild to severe burns, may damage toilets, and possibly other hazards.

If you plumb in a hot water circulation pump, we highly recommend that you choose a normal circulation system that utilizes a dedicated return line -this prevents the hot and cold water cross connection. Click here for recirculating systems that use a dedicated return line.



Frequently Asked Questions

Q. "How does the Comfort Series hot water system work?"
A. Grundfos "Comfort" series hot water system works in the following manner: The comfort valve is installed under the faucet farthest from the water heater. The UP 15 series recirculation pump moves the hot water from the heater throughout the pipe back to the heater through the cold water line. As the water heats up at the comfort valve, it closes. When a faucet is turned on, warm water is instantly available for use with no waste.

Q. "I'd like to have hot water without much of a wait. How can I do this?"
A. The two easiest solutions are:
A) A tankless water heater at the source.
B) A hot-water recirculation system. This consists of a small pump and a return line from your farthest fixture. The pump mounts near the bottom of your water heater along with a swing check valve (see diagram found on our circulation pump page).

Q. "Does a hot water recirculating system use up a lot of energy?"
A. Both options use energy. But not as much as most people think. On the recirculating system we highly recommend insulating all of your hot water pipes. Also having a timer and/or a thermostat will use even less energy. An electric tankless water heater doesn't use any energy when you're not drawing hot water.

Q. "I have multiple hot water branches. If I use the UP15-10S series, how will I get water to all branches?"
A. You can order additional comfort valves for each branch.

Q. "What is the benefit of installing an optional timer or thermostat?"
A. Either one will save energy (and money). The timer only allows the pump to turn on at certain times. So if you only need hot water in the morning, you could set the timer for 6am to 8am. Then the pump would only recirculate the hot water during that time. The thermostat turns off the pump when the water in the pipes reaches a certain temperature. So once the water in the pipe is hot, the pump turns off. When the timer and thermostatic controls are installed together, in series, the circulator operates ONLY at the preset clock times specified by the user AND ONLY when the temperature conditions of the thermostat are met. That is, if either the timer control or the thermostatic control switch is open (off), the circulator will not operate.



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