recirc is my preference
Hello all,
My kitchen sink and dishwasher are located about 35 pipe feet from the water heater, so it takes probably 45 seconds to deliver hot water at the tap and dishwasher. To reduce the lag time, I am considering installing, under the sink, either (1) a small tankless booster heater or (2) an on-demand recirculation system such as D'Mand.
Can anyone tell me the pros and cons of these options?
An undersink electric tankless is impractical unless you can easily install a 100 amp circuit. An electric undersink tank is reasonably practical, but you'll pay to heat both the electric tankless, and the water drawn through the gas tankless both. Not as energy efficient as the gas tankless alone.
I chose the gas tankless with recirc solution, and am paying only 0.5 therms per day (about $13/month) for hot water with a family of four. My heater is 65 feet from the kitchen! I use a
Redytemp recirc pump which includes a very flexible timer configuration. This way, no button push is required for the common use times of morning and evening, but hot water is still available at any time via the Leviton rocker switches in the kitchen and each bathroom. I think with a tankless one should not use a full-time circulator that would cycle the heater every 15 - 30 minutes 24/7, even though modern tankless are warranted for use with recirc pumps. Obviously, efficiency would suffer without the use of a timer.
My only regret is I wish I had got the larger version of the recirc pump and used a 3/4" (instead of 1/2") dedicated return to speed the purging of cold water from 20' of 1" pipe, then 45' of 3/4" pipe. That's a lot of water, and it takes 1-1/2 minutes if it is stone cold.
If you consider recirc, important features are a combination of timer,
adjustable thermostatic, and pushbutton control. A dedicated return line is ideal. If completely impractical, the best use of the existing cold line as a return requires a positive action solenoid valve to isolate it when not in use, and prevent thermosiphoning and always having warm or hot water in the cold line. Not all recirc systems use this type of valve, but use a cheap check valve. Lastly, you want a standard, easily replaceable pump.
Hope this helps.