The Watts Premier Hot Water Recirculating System

According to Watts, the Premier Recirculating system gives you hot water instantly at every faucet. Here's the quote from their website: "Watts Premiers Hot Water Recirculation Pump brings convenience and saving to your home, giving you hot water instantly at every faucet, when you need it."

Technically that's not really true...

A luke-warm water circulating system

The Watts Premier system is what I like to call a luke-warm water circulating system. The system consists of a valve for placement under the sink, and a pump located at the water heater. The pump creates a pressure difference between the hot faucet and the cold faucet.

The valve connects between the hot and cold faucets, and when the temperature drops to below 98° water flows through the valve bringing the heated water towards the sink/faucet/valve installation.

When the valve senses a temperature above 98° the valve closes and the flow stops. In other words it operates identically to a traditional temperature controlled circulating system, except instead of hot it circulates warm water, and of course, uses the cold water line as the return line.

Wasting energy

The water may not be hot, but it is much warmer than with no premier system, consequently your water heater will have to consume more energy to keep the water in that big heat exchanger you call your plumbing system warm.

One nice thing about the Watts pump is that you can place a valve under every sink if you wish, and get instantly warm water to any or every fixture. However, you will at the same time increase the energy consumption of your system.

Won't work with tankless water heaters

The pump is very small and does not consume much energy, however as a result it can't pump much water either. It's unlikely that the Watts Premier will be able to turn on even a small tankless water heater. According to the pump curves on the Watts website the pump cut-off pressure is about 1.5 psi.

Watts uses a Grundfos UP15-10SU7/TLC pump with a 1/25 horsepower motor which consumes 25 watts. The pump runs continuously, so running it for say 16 hours a day would consume 25 watts/hour x 16 hours/day x 365 days/yr = 146,000 Watt/hours per year in electrical energy consumption. That's 146 kWh and at say 13 cents per kWh would be $19.00 per year. This would be substantially less than the energy lost due to circulating warm water.

The hot water will of course arrive more quickly than if the pipes were allowed to cool down completely because being colder, they would suck more heat out of the oncoming cold water as it flowed to the faucet. But it certainly can not be called "Instant".

The listed price for the Watts Premier system on its website is $225.00

The Metlund D'mand Pump

The Metlund D'mand system is a demand type hot water delivery system. It only pumps the water to the fixture when you "demand it" by pressing a button. The D'mand pump mounts under the sink, and connects to the hot and cold water supply valves like the Watts valve. A power outlet is needed to plug the pump into.

When the button is pressed the pump begins pumping the water to the fixture returning the cooled off water in the hot water pipes back to the water heater through the cold water pipes. When the pump detects sudden increase in temperature it shuts off so hot water does not get into the cold water line.

No wasted energy

Since all the pump does is fill the pipes between the fixture and the water heater with hot water just as you would do by running the faucet, you don't use any additional energy from the water heater with the system. Since the pump runs for a very brief time, it uses far less electricity than the Watts pump, about $1.00 per year.

Works with any tankless water heater

Some models will work with tankless water heaters. Since tankless water heaters typically take 10 to 20 seconds longer to get water to the fixtures, the Metlund pump is a very nice accessory for any tankless water heater, gas or electric. You get your hot water very quickly with no additional energy penalty and you save a lot of water.

The Metlund pump models range in price from about $350 to about $750 retail price.

Metlund D'mand System compared with Chilipepper CP6000 pump: Metlund D'mand Info

Useful information about water heaters including tankless hot water heaters: Storage Water Heaters Instant hot water systems.