There are so many hot water pumps and hot water distribution systems on the market that it can be a daunting task to figure out which one is the best for your application. Here I will examine each type of hot water pump or system and present the information in a meaningful way so you can determine which system is right for you.
Hot Water Circulating Systems
Historically larger homes have often been equipped with hot water circulating systems to provide instant hot water at the fixtures. These systems have a small pump designed to pump hot water connected between a return line from the last sink and the inlet of the water heater. The pumps have very low power because they are designed to run 24 hours a day and they only need a very low flow rate to keep the water in the hot water pipes hot.
The problem with traditional circulating systems is that they waste tremendous amounts of energy. Your hot water plumbing layout is like a big radiator. Continuously circulating hot water through the pipes causes your water heater to have to replace the lost heat and that increases the energy consumption and your utility bill substantially.
The pumps don’t have the power to produce enough flow to turn on tankless water heaters, so you need a storage water heater to work with these older types of systems.
Manufactures of traditional hot water recirc pumps include Grundfos, Taco, and Bell & Gossett. Typically the horsepower ranges from 1/40 of a horsepower to 1/8 horsepower for residential plumbing systems.
Warm Water Circulating Systems
There are a number of systems on the market today that circulate warm water through the piping to keep warm water at the fixture. These systems usually do not have a return line, using the cold water line as the return.
The manufacturers of these systems often call them “Instant Hot Water” systems and claim you will have instant hot water. Actually it’s instant warm water. They do pretty much the same thing the traditional system did but with a lower temperature and the cold water lines as the return.
The pumps are nearly identical to the traditional type circ pumps and some systems actually use traditional circ pumps with an electronic controller.
They, like the traditional systems, use a lot more energy than a standard non-pumped plumbing system. The water heater still has to burn more often to replace the lost heat. By using the cold water line as the return, it too will now have above ambient water temperatures and you will have to purge the cold water pipe of warm water if you want a drink of cold water. That will be water you will be running down the drain, not a very green system.
The last problem I have with these types of systems are that they still don’t give you “hot” water when you turn on the faucet, the water is warm, not hot. So if you really do want hot water you still have to run the water down the drain to purge the warm water from the line.
Circulating systems that fall into this group include Grunfos (comfort system), RedyTemp, Watts Premier, Laing Autocirc, and Armstrong Express.
Most of these systems do not have enough power to operate a tankless water heater.
Hot Water Demand Systems
Hot water demand type systems use the cold water line as a return line, and usually locate the pump at the furthest fixture from the heater similar to the previous systems. However demand systems do not continuously circulate water, they only run when the user demands hot water by pushing a button. This activates the pump, which then turns off when hot water reaches the fixture.
You don’t have “instant hot water”, but it’s nearly instant when you turn on the faucet, so you don’t run any water down the drain. The water heater does not run any longer than it would with a standard plumbing layout without a pump, so you don’t use any additional energy. Because the pump only runs a few seconds, typical energy costs run about $1.00 to $2.00 per year… not very much.
Typically these systems will deliver your hot water to your fixtures in less time than running the faucet full blast, and you feel good every time you use hot water because you know you are being green and reducing your carbon footprint.
Tankless Water Heaters
Demand systems work great with tankless water heaters since they don’t circulate the water and most demand systems have the power required to turn on tankless units.
Tankless hot water takes longer to get to your fixtures than if you had a storage water heater since the tankless heater must heat the water first, and typically requires 10 seconds or so longer than a storage heater.
Manufacturers of hot water demand systems include Chilipepper Sales, Metlund Demand Pumps, and Taco which uses a licensed version of the Metlund system. The Metlund systems actually use traditional Taco hot water circulating pumps, and only the larger models can run tankless water heaters.
If you are considering going green and reducing your carbon footprint, consider installing a hot water demand system in your residential plumbing system today. Save water, save time, and save money while being eco-friendly to your planet.