For years installers have been using the drain port of tanks as a “cold” supply to feed external heat exchangers. While this can work it has a number of drawbacks. One of which is that any sediment in the water coming into the home through the hot water tank will accumulate in the bottom of the hot water tank. This sediment will accumulate first around the bottom edge of the tank. When you use the drain port as a supply you are pulling the dirtiest water in the system which can lead to premature clogging of filter screens (which you better have) and unnecessary wear on the your pumps. But, there is a better way…
On tanks equipped with two top ports (hot and cold) and a top T&P valve you can reconfigure the T&P port to accommodate both the T&P valve as well as the hot out. This frees up the port marked for hot out to be used as the solar hot water return (in conjunction with a diffusing dip tube (part # P-DT-955)). Now, you place a tee on the cold water inlet and use that to supply cold to the solvelox. By pulling the cold water up the cold water dip tube you are avoiding any of the sludge that can plug up your system.
By using this technique you are able to have the advantages of a four or five port tank without the cost and aggravation of finding that tank. (see picture) In using this technique be sure that the T&P probe protrudes into (but not past) the top 6” of the tank. If needed ask for a T&P with an 8” long probe (part # P-V-3PT76XL).
