Domestic Hot Water Return Pipe Sizing

The length of a pipeline inclusive the circulation line is 100 m.

Domestic hot water return pipe sizing. This prevents galvanic corrosion due to dissimilar metals in contact. Minimize elbows and fittings but try to follow the path of the hot water supply line which should have a minimal number of elbows and fittings anyway. The friction loss for this diameter supply pipe will be about 1 4 ft per 100 ft according to the system syzer. A 006 when there s a 200 400 loop length.

Let s say there are four 2 hot water risers at 80 feet each and each riser at each floor has about 100 feet of run out using pipe less than 1. With water at temperature 50 oc the average specific heat loss from the pipe line is estimated to 30 w m. Piping should be insulated. High water velocities combined with hot water can cause velocity erosion issues for the pipe and valve walls.

Hot water does have a 5 ft second maximum so piping should be sized accordingly. Recirculation pipe material should be the same as the hot water pipes used. A sizing calculator i e. Taco recommends a 003 when the loop length is under 200.

We always like to install a return line. The minimum pipe size i use for the hot water return system piping is inch pipe. Recirculating system piping and heat traced piping shall be considered to be sources of hot or tempered water. Taps with a maximum flow rate of 5 or 8 litres per minute don t need large diameter pipes and switching from a 15 mm pipe to 12 mm or even 10 mm can dramatically reduce the volume of water that needs to be flushed through.

A typical water heating system will circulate around 1 gpm for each loop. Q 100 m 30 w m 3000 w. Water flow velocity is very important in domestic hot water pipes with copper piping and brass or copper alloy valves. Not only does it reduce the drag on the pump or gravity circulation it increased tha capacity of the hot water system by the amount of water in the pipe 0 0269 gal ft.

Determine pump head select pump. The developed length of hot or tempered water piping from the source of hot water to the fixtures that require hot or tempered water shall not exceed 50 feet 15 240 mm. For 1 87 gpm we would choose a copper pipe. Hot water recirculation systems consist of one or more loops typically one loop per floor.

System syzer can be used to size the return line. Let s assume the hot water mains are 4 in the basement and about 300 feet long. The total heat loss from the whole pipe line can be calculated as.