Time to replace my 18yr old State nat gas water heater. I have a Weil-McClain nat gas boiler w/83% efficiency. Does it make sense to install an indirect water heater w/only 83% efficiency?Thanks

In my opinion, no. But it depends on a lot of factors. Repiping boiler to tank, and BTU output of boiler. You would also have to have some electrical work done, so that domestic hot water heating would take priority. In the long run, I think you will be best replacing the old water heater with a new one.

I have one bit of information for you to think about. I seem to be the only plumber on this site having this problem but I am having problems with the anti-explosion screen getting stopped up and it is very hard to clean. Of course State is no longer, they were bought out by A. O. Smith but they are having the same problem. I am having the best luck with Rheem but again it also is causing some problems.

Taking this into consideration you might want to do away with the water heater all together, but I would consult with some other plumbers first.

Tellu, I have experienced this problem over and over again. We also just recently switched from ao smith to rheem(due to their honeycomb filter plugging). Got tired of being told not to break the honeycomb out, when it was the only real fix. In my opinion, they should have let well enough alone, instead of mandating sealed combustion water heaters. The efficiency isn't any better. This is a clear case of someone overthinking, and coming out with a rule that makes new water heaters problematic. I would bet that all gas fired appliences will be sealed combustion within the next 5-10 years. God help us all. I just wonder how they will get appliences like stoves to be sealed combustion.lol.

Anyway, I still think the replacement of regular water heater should be done(in this instance) with a new regular water heater. The only problem I see with the indirect water heater is that if you boiler goes down, you now don't only have no heat, but you also now have no hot domestic water.

Thank you for the responses, so what brand of water heater - direct - would be recommended w/the existence of the aforementioned problems?

As of now,(and I'm new to them, but they seem about as good as it gets at this time) I would suggest a rheem. Or have you thought at all about tankless water heaters? There really are a lot of options out there for heating water these days. You may even be happy with a indirect. I guess what I'm saying, is its six of one, half dozen of the other. Are you planning to do the install yourself, or are you hiring it done. If hiring it done, I would get three bids(and advice from at least three different contractors). Ask them all the questions you have on your mind, and tell them about any concerns. Let them know that you are open to suggestions. They will be able to look at your boiler system and tell you if this is a good idea or not(for your system).

Really all we can do for you at this point is give suggetions, I really think you will be happier talking to someone in person. Good luck and please let us know what you decide. Take care.

3 is my magic # for quotes. I just wanted to get a few unbiased opinions from experienced individuals who have nothing to gain from their answer, except thanks! I am hiring someone to do this and want to have all my info available to explore options. I have eliminated tankless.
Thanks, I'll post some feedback when I get it replaced in the next couple of weeks.

Look forward to it. Take care.