hot water recirc

David Efflandt

I have worked with engineers on hot water recirc in high rise buildings and it needs to be planned from the start with a well insulated loop that runs close to the fixtures. Where they tie together from different floors they use circuit setters (or other throttling method) to balance different zones. The point is to keep just enough hot water circulating in each loop so any fixture gets hot water quickly. The recirc is a closed loop, so it does not consume water, it just pumps it back where it got it from (evenutally back to its own suction). Water used by fixtures is replaced from the supply.

If someone retrofits domestic hot water recirc to an existing system that is sprawled out and not well insulated, it may wind up being an uncontrolled radiant heating system. And fixtures distant from the circulating loop might still not get hot water quickly.

Bob C.

hot water recirc

I was thinking the other day…… how does a plumbing system with multiple hot water recirc lines circulate water? Most of the jobs I see have a ½ line chasing the hot water out to the fixture. Then they are tied together, usually with an accessible ball valve for balancing them. They all run back to a ½ main that runs back to the boiler room and are connected to a good size pump. When no one is using the water and the aquastat is calling isn’t this system similar to a heating system in the sense of circulation. Say the main is 100ft long and at the end of the main you have a 50ft run out to a fixture. In the middle of the main you have 2 -70ft run outs in either direction. Then right at the beginning of the main you have a 100ft run out. All the lines are ½” how in the world does this circulates all the run outs. I have seen it work but I can never figure out how. After reading a lot of Dan’s I would think that the water would go for the least path of resistance. I understand that balancing the lines helps but wouldn’t you eventually run out of capacity, and start stealing cir from other branches? Then when you go back to them you steal it from some where else? Just one of those things that I wonder how they work

Bob Cat