Kind of reminds me of my kitchen sink drain. Wife said water will not go down. I tried all kinds of things to un-plug the clog, including running a manual operated snake. No success. I ran out of time, so hired my brother(Handy Man) to come unclog the 2" kitchen drain line. He was un-successful. We each had lots of time trying to un-plug the drain line. Finally, we decided to cut the drain line. WOW!, the 2" drain line was plugged solid, the whole 10' or so with grease. Wife was dumping all the grease she could find, down the kitchen sink. If I would have known that to begin with, It would have been a fast easy fix. Instead, we had many hours into trying to clear a 2" PVC drain line, packed solid with grease. Needless to say, she doesn't dump grease down the drains any more. There's a reason why I always said NOT to dump grease down the drains. Now she knows the reason. By the way, I Thank You All for your "heat exchanger" replies. OliverLu47Dan wrote:If a heat exchanger is sized right and installed correctly than efficiency will be quite high.
One thing with plate type heat exchangers that are installed to make DHW, is water chemistry. If you are going to run a plate type with water that is high in minerals, you will end up with it plugged up. I used to clean plate type heat exchangers for a couple of friends who had OWB's set up to make their hot water. After several seasons of this they got water softeners installed to take care of the problem.
If they had installed a shell and tube heat exchanger they could have had a drain valve installed on the shell and then blown out the buildup.
With a plate type it is tough to get the build up out of all the plates, I had a system that pumped CLR through them, the pump could produce pressures up to 100psi.
One year I had to trouble getting then one heat exchanger to flow anything. After soaking for weeks in an acetic acid bath, and several attempts to push the acid through. I made a stand pipe to hold the acetic acid, I connected the stand pipe to the exchangers outlet spud and set it on the ground. Set up my ten foot step ladder and then attached the pipe to the ladder with a bungee cord, climbed up and filled the stand pipe with acetic acid and let it set for a few days. I had a shorter stand pipe on the inlet spud. I kept the stand pipe full of acid and when the acid migrated to the shorter stand pipe I knew that I had at least one passage opened up. I made another set of stand pipes that I could fill and let set on my one work bench. I would drain out the acid and fill the pipes with fresh acid once they stopped bubbling. I ran through four gallons of acid and it took three months to get the heat exchanger cleaned out.
Was it worth the bother, no it was not. He probably spent more money saving it than it would have cost to replace it with a tube and shell type. I have two Shell and tube heat exchangers from a dumpster dive. that I plan on using on my system eventually. Both are a little too big for their purpose but should work out.