Domestic Water Recirculation Systems Part 4: High Rise Considerations

RL DeppmannMonday Morning Minutes, Pumps, Plumbing System Design, Domestic Water Recirculation, Balancing

The last three articles outlined pump selection in domestic water recirculation systems. In general, these systems have low flow and low head pumps. What happens in a high rise with pressure reducing valves (PRV) in the hot water supply? The pressure reducing valve introduces a fixed pressure drop which must be added to the calculations.

Domestic Water Recirculation Systems Part 3: Pressure Drop

RL DeppmannMonday Morning Minutes, Pumps, Plumbing System Design, Domestic Water Recirculation, Domestic Water Recirculation

The purpose of the domestic water recirculation system is to delivery hot water near a fixture during times when there is no draw. If someone is using hot water in the next room or apartment or process; the hot water is near enough to your fixture so the hot water is delivered in seconds, not minutes.

Plumbing Topic: Domestic Water Recirculation Systems Part 2

RL DeppmannDomestic Water Recirculation, Monday Morning Minutes, Plumbing System Design

Let’s assume the domestic hot water supply is a total length of 1000 ft. That is the entire pipe on all of the floors. Let’s also assume an average of 15 BTU/hr/ft of loss through the supply pipe insulation. Now let’s assume the recirc piping is 300 ft total at an average of 10 BTU/hr/ft of loss. What flow rate is required for a 10 degree ΔT? What flow rate is required for a 5 ΔT?

Domestic Water Recirculation Systems Part 1: Flow Rate

RL DeppmannMonday Morning Minutes, Plumbing System Design, Domestic Water Recirculation

The R. L. Deppmann Monday Morning Minutes series will focus on the plumbing portion of the new construction and building facility business for the next few months. The topics will be domestic water recirculating systems, pressure booster systems, volume and instantaneous water heaters, and mixing valves. I’ve had 6 job site visits in the last 2 months to help engineers, service contractors, and facility managers solve problems with domestic water recirculating systems. It seems this is a good place to start.