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Grundfos 99452459 Review


Unlike other hot water recirculating pumps form this product class, the Grundfos system features a Retrofit solution, which means that it doesn’t require a return line. With this unit, Grundfos has introduced an innovative easy programmable digital timer intended to help pull back water to be heated and recirculated. This explains why no return line is needed. If you want, you can use a remote electrical switch instead of the timer. Just remember to provide a ground connection to the remote switch.

Another useful feature of this unit is the thermostatically controlled comfort valve. If you install it to the faucet, furthest from the water heater, it will help regulate the flow from the hot water line to the cold water one. There is a thermistor in the comfort valve, which allows only a trickle of hot water to go into the cold line.

The housing of the pump is made of stainless steel, which is a durable material. A user-friendly display helps you to set the desired temperature and time. What makes this product unique is its battery back-up, which ensures that even when the electricity goes down, you can still have hot water on demand.

What Does It Do?

Grundfos 99452459 Instant Hot Water Comfort Recirculation SystemThis Grundfos system provides instant hot water to all the faucets and appliances at your home. As the pump keeps the pipelines filled with warm water, you can immediately wash your hands or shower with water coming at a pleasant temperature. How does the pump manage to do so? Well, it keeps the liquid moving in circulation with the help of a valve installed at the faucet furthest from your heater. Of course, you need to bear in mind that since the water comes from the heater, its temperature will gradually increase.

If you have this pump for a year, you will notice that it is a very agreeable and low-cost solution, especially if your water heater is far from the faucets in your household. It has been estimated that this Grundfos product saves up to 12,000 gallons of water annually. Please, keep in mind that it is not advisable to install this unit to tankless water heaters as they have a high-pressure drop, which this pump cannot handle.

The Content of the Set

  • A digital plug-in timer,
  • A thermal bypass,
  • A 10ft line cord,
  • A hose kit


Voltage: 1×115 volts

Motor Watts: 25 W

Weight: 6,69 pounds

Dimensions: 9 x 8,8 x 6,3 inches

Batteries included: yes

The material of the pump housing: stainless steel

Liquid temperature: 36 to 230 degrees

What to Expect?

This unit’s installation can be done in less than two hours if you follow the instructions and the diagrams that come with the product. Moreover, operating with it is also not a challenging task – the only thing you need to do is control whether the pump is on or off, which is done by the timer. There are no speed settings to worry about. Once it is in operation, you will not hear it vibrating as it is a very quiet unit. So if your heater is situated where you can hear it, this pump won’t add to any noise level. In case any of the parts or accessories that come with the pump get damaged, you can easily replace them as this unit is compatible with other Grundfos line cord products.


  • Installing this pump is a snap, and everything necessary for it comes with the product. You don’t even need a plumber to do it for you. So you start saving money from the very moment of mounting the unit.
  • You shouldn’t worry if any of the parts of this unit don’t function anymore. You can replace them with parts from other Grundfos line cord products.
  • If there is a power cut, you can still have hot water whenever you need it as the pump has a battery back-up.
  • This system can save up to 12,000 gallons of water per year, which turns out to be a very low-cost solution.


  • As this pump cannot handle a lot of pressure, it can’t be used with tankless water heaters.
  • Your cold water will come out warm at the faucet, but it will become cold again in less than 10 seconds.

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