I received good feedback from this forum on another DIY project (hydronic toe-kick heat), so I'm now looking for some more guidance. This time, I'd like to get hot water faster to my kitchen and/or bathroom, with minimal water waste and expense.
Current setup: I have a reasonably-efficient oil-fired boiler with a domestic hot water coil (Weil-McLain WTGO series 3- installed 2004). I'm not looking to replace the boiler. The total piping distance from the boiler to each location is ~40 ft of 3/4" copper pipe. The first 20 ft of those distances is shared. Most piping is accessible in an unfinished basement.
I'm considering these options: 1) Unheated Storage Tank, 2) Heated Storage Tank, 3) Circulator Loop
Option 1 - Unheated Storage Tank
I could position a well-insulated tank so that it is 15 ft from the kitchen and 20 ft from the bath, thus reducing the distance for hot water to both delivery locations. Concern: Even though insulated, the water temp will slowly drop in the tank. When this happens, even though "warm" water would be delivered quickly, it may take even longer for "hot" water to be delivered. The larger the tank, the longer for water to go from warm to hot, wasting water in the process.
Option 2 - Heated Storage Tank
Same location as option 1, but make it a smaller electrically heated tank. This would mitigate the warm-to-hot issue with the unheated tank, but will require greater up-front expense and operating cost. If this makes sense, what size tank would be appropriate.
Option 3 - Circulator Loop
I have not seen this described anywhere, but it seems do-able. Create a well-insulated, low-flow circulator loop with a controlled valve just before the kitchen. When hot water is called for, or if the water temp at the valve is at or above x-degrees, do not circulate, but allow water to be delivered. When hot water is not called for, if the water temp at the valve falls below x-degrees, circulate water through the loop back to the boiler inlet point until target temp is achieved. This should deliver the hottest water fastest to one location. If the other location is branched off the loop anywhere, it will still benefit somewhat. One concern- even with insulated pipe, the heat loss will probably be faster than with either storage approach, and the boiler may fire more often.
Any feedback or alternate recommendations would be appreciated.