Hot water demand systems are specialized circulating systems for use when there is not already a hot water return line. They are systems designed to pump your hot water from your water heater to your fixtures fast without running water down the drain.
Your cold water line connects to the inlet of the water heater. Your hot water line connects to the outlet of the water heater. So if you connect a pump between your hot and cold water lines you can pump the water in a big circle.
A hot water demand system pump connects between the hot and cold water lines at the sink furthest from your water heater. When you desire hot water you push a button that starts the pump. The pump sends the water through the hot water piping to the pump, and the cooled off hot water that was in the hot water piping is send back to the water heater inlet through the cold water piping.
When the pump senses an increase in temperature, it shuts off, preventing hot water from getting in the cold water line. If the pump is strong enough, you can get your hot water faster than running the faucet.
Demand systems use very little electricity, costing typically between $1.00 and $2.00 per year to operate.
Let’s compare two such systems, the Metlund D’MAND System, and the Chilipepper CP6000.
Metlund D’Mand Systems
The Metlund D’MAND system has three different models with different horsepower ratings. The bigger the horsepower rating is, the faster the flow rate.
The first model, the S-50 sized one, has the lowest power and the lowest price at about $339.50 for the S-50T-PF-V-102. According to the Metlund website it is not recommended for tankless water heaters. The S-50 has 1/40 horsepower. The performance of the S-50 is listed as having a maximum flow rate of 8 gallons per minute with a maximum pressure of 10 feet of head. 10 feet is equal to about 4.3 psi.
However this is a bit misleading. In order to pump 8 gallons per minute the pump cannot have any back pressure, so the outlet can not be hooked to anything.
With only 4 psi the pump can’t pump much water through even a straight piece of pipe. Only at zero psi backpressure can the pump push out 8 gallons per minute. With the given information it’s impossible to tell what the flow rate would be when it is installed in a plumbing system.
Metlund suggests using it for runs of less than 50 feet, and it has a 3 year warranty. You have to use full 1/2″ fittings to plumb the pump in because there isn’t enough pressure to pump much water through the small restrictions in the angle stop valves under the sink.
Metlund Model S-70T
The next larger model is the S-70T. The website recommends the S-70T for pipe runs shorter than 60 feet when used with a tankless water heater and up to 100 feet with a standard water heater. The S-70T motor has 1/25 horsepower. As with the other models this unit requires full 1/2″ piping connections and the warranty is 5 years.
This pump is rated at 14 gallons per minute and 16 feet of head. The 14 gallons per minute has to be done with 0 psi back pressure, and at 16 feet of head (7psi) the output flow drops to zero. Retail Price: about $441.50.
Metlund Model S-02
The largest model, the S-02, again with a listing of 28 gallons per minute and 30 feet of head (13 psi), has 1/8 horsepower. As with the previous models this one requires full 1/2″ plumbing connections. This model weighs 16 pounds.
The S-02T-PF-V-102 has a list price of about $759.50, and the warranty is 5 years.
All three models list a life expectancy of 15 years, and shut off when a temperature increase of 3 to 4 degrees is detected at the pump.
All three models are available on Metlund’s website.
Chilipepper Sales only manufactures one model, the CP6000 which has a powerful 1/3 horsepower motor. It produces a maximum pressure of about 60 psi (138 feet head), and has a maximum flow of about 4 gallons per minute. (with no back pressure)
The Chilipepper was designed to be connected to the plumbing with standard hoses used for connecting the faucets to the shut-off valves. That way you do not need to turn off the water to the house. All you need to do is turn off the shut-off valves under the sink, and connect up the hoses.
The horsepower is needed to force the water through the tiny (less than 1/4″ dia.) openings in the hose connectors. Since nearly all the pressure is used to overcome the pressure drop created by the small holes, the Chilipepper nearly always pumps 2-3/4 to 3 gallons per minute no mater what the piping situation.
The CP6000 is 7-1/2″ long x 4-1/8″ wide x 3-1/2″ tall making it substantially smaller than the smallest of the Metlund units. It is also lighter at about 4 pounds.
To achieve the small size and big power the CP6000 uses a brush type motor. The brushes will wear out after about 500 hours of operation. If you use your pump 5 times a day 365 days per year, and it runs 1 minute each time (100 -150 feet), then you will accumulate about 30 hours per year. So you could expect your pump to last about 16 years. A new lip seal and a new set of brushes will get it back up and running again.
The CP6000 has a maximum run time of 3 minutes. If it doesn’t detect an increase in temperature within 3 minutes it will shut off. The reason for this is that if the water heater breaks down, there would never be an increase in temperature to shut it off and it would run forever.
To determine the maximum distance from the water heater that can be handled by the Chilipepper, we need to see how far the water would be pumped in 3 minutes. This will depend upon your plumbing. Since the pump produces a flow of about 3 gallons per minute no matter what size the piping is. The smaller the pipe the faster the water will flow.
For an example, at 3 gpm the water velocity in 3/4″ inch diameter type L copper pipe would be about 2 feet per second. In type L 1/2″ pipe the velocity would be about 4 feet per second. Therefore, assuming the worst case, that the house is plumbed entirely with 3/4″ pipe, the maximum distance your fixture could be from the water heater would be about 360 feet. If plumbed entirely with 1/2″ dia. pipe, the distance would be 720 feet.
The CP6000 has an unconditional 30 day money back guarantee, and it can be returned for a full refund for with no questions asked.
The CP6000 has an adjustable temperature sensor so you can set the unit to turn off when it senses a temperature of 3 to 12 degrees, allowing you to fine tune the arrival of hot water to your liking.
The CP6000 retails for $179.99 on the Chilipepper Website.
Both Metlund and Chilipepper have code approvals.