aerie
Member
I am making a heat exchanger for my shower trap arm. I have a 2" section of copper drain pipe that I want to coil the incoming water supply line around, before the supply feeds into the 3/4" inlet of my on-demand water heater. I already tried and failed at coiling 3/4" soft copper tubing around it. I see in the commercially available ones (pictured), the supply line is split into multiple smaller lines which has the advantage of more surface area for contact in addition to the smaller diameter tubing being more workable. I'm considering this approach but am wondering if there are any implications for downstream pressure or flow when splitting a line into multiple smaller lines and then rejoining them before feeding into the water heater. According to the table linked below, splitting into two 1/2" lines would maintain the same cross-sectional area as the single 3/4" line. The commercially available ones split into four lines but according to the table linked below, there is no diameter of pipe that will quadruple to match 3/4" cross sectional area. Is it better to have the cumulative cross-sections of the coiled lines exceed that of the 3/4" pipe so the coiled volume acts as a sort of reservoir?
I'm leaning towards two 1/2" lines because the tubing and fittings are easy to find at it would only require one tee on each end. Lastly, can anyone comment on whether it is reasonable to expect to coil 1/2" around a 2" diameter (wish I had asked about 3/4" before trying it).
Also, not sure if this is relevant but the heat exchanger is the only portion of my plumbing system that will be copper. The supply line will be pex before and after the coil and the rest of the DWV system is ABS.
*cross-sectional areas were taken from this chart: Copper Tubing Size Chart ASTM B-88 | Engineers Edge | www.engineersedge.com
thanks, aerie
I'm leaning towards two 1/2" lines because the tubing and fittings are easy to find at it would only require one tee on each end. Lastly, can anyone comment on whether it is reasonable to expect to coil 1/2" around a 2" diameter (wish I had asked about 3/4" before trying it).
Also, not sure if this is relevant but the heat exchanger is the only portion of my plumbing system that will be copper. The supply line will be pex before and after the coil and the rest of the DWV system is ABS.
*cross-sectional areas were taken from this chart: Copper Tubing Size Chart ASTM B-88 | Engineers Edge | www.engineersedge.com
thanks, aerie