Water Heater Pumps, Hot Water Circulating Systems, Warm water Circulating Systems, and Hot Water on-demand Systems Compared and Reviewed 

The following articles involve hot water pumps for water heaters, both storage tank type heaters and tankless hot water heaters, hot and warm water circulating systems, and compares and reviews several hot water on-demand systems.
 

The Astro Express Hot Water Recirculation Pump- A Product Review

The Astro Express System, manufactured by Armstrong is what I refer to as a warm water circulating system..  It's similar to the Grundfos Comfort system. A typical recirculating pump is mounted at the outlet of the water heater so that it pumps hot water out of the water heater and through the hot water piping to the valves under the sinks.

An Astro Express Valve connects between the hot cold water lines under each sink.  This valve between the hot and cold water lines creates a "loop"  through the hot water piping, the valve, the cold water pipe, and back to the water heater.
 

Metlund d'mand ® System VS Chilipepper Sales CP6000

The Metlund d'mand ® system consists of three models with different size pumps. The bigger the pump the faster the hot water flow rate. The S-50 model has the lowest power and cheapest price at about $339.50.  Metlund does not recommended it for tankless water heaters. Metlund suggests using it for runs of less than 50 feet. You have to use full 1/2" fittings to plumb in the pump.
 

The Laing Autocirc1 warm water circulating system.

The Laing autocirc1 is a cold-water-return warm water circulating system. It uses the cold water line as a return line and circulates hot water through the piping keeping the water at the fixture between about 85 to 95 degrees roughly.  Tepid water.  The cold water line will no longer be full of cold water, it will be warmish.  To get really hot water you still have to wait, and if you want really cold water you have to wait then as well, which may lead to wasting water.
 

Metlund d'mand ® S-50T Hot Water d'mand ® Pump vs. Chilipepper CP6000 Hot Water Pump 

Comparing the Metlund and Chilipepper Hot Water on-demand Systems. This article compares the Metlund d'mand ® system model S-50T, to the Chilipepper CP6000.  If you have a tankless water heater that supplies a fixture 50 feet away, the Metlund model S-05T would not be able to produce enough flow to turn the unit on. The Metlund S-50T-PF Kit ($356.00) Comes with two 1/2"" threaded male adapters  two brass "T" compression fittings, two stainless steel flex-lines, and one hard-wired button.
 

Watts Premier Recirculating Pump vs. Chilipepper CP6000 

The Watts Premier Hot Water System, a comparison between the Watts Premier hot water pump to the Chilipepper on-demand pump. The Watts Premier system provides faster hot water but it isn't instant by any means. The Watts Premier system is a luke-warm water circulating system.  It uses a temperature sensing valve and a continuous running pump to circulate warm water through the house plumbing.
 

Hot Water Pumps, Metlund, Grundfos, Autocirc, RedyTemp, Taco, Armstrong, Chilipepper, and Watts Premier

I will examine the various types of hot water pumps or systems and you can make a better informed decision about which pump is best suited for your needs. I'll deal with traditional hot water recirculating systems, warm water circulating systems like Autocirc, RedtyTemp, and Watts systems, and hot water on-demand systems such as Metlund and Chilipepper.