Leaving hot water heater turned on (AC)

Nov 16, 2012
1,037
Catalina 310, 2000, #31 31 Santa Cruz
I didn’t find anything about this with a quick search: are there any issues with leaving the AC power for the water heater turned on when the boat is only being used weekly or so? Would the hot water cause the anode to wear more quickly, or stuff to grow in the tank or lines and produce stinky water?
 
Feb 26, 2004
22,759
Catalina 34 224 Maple Bay, BC, Canada
Rob, there is no reason to do that. It only takes 15-30 minutes to heat the water. Then turn the AC OFF. No need to keep running power to already hot water, plus you're depending on a thermostat to keep it from overheating. In my new neck of the woods, it takes 30-40 minutes to heat the water 'cuz our ocean here is 47F, cooler than your 57F. I can be patient and wait that long...:)

If you get into the habit of using the hot water faucet even when your heater is off, you'll keep water moving thru the ehater and avoid any stagnation.
 
May 17, 2004
5,026
Beneteau Oceanis 37 Havre de Grace
I don't leave mine on while I'm away for the week. Just too much chance of something failing with nothing to be gained. I do turn it on when I first get to the boat, and leave it on until I leave. I suppose I could turn it off after the water heats up as Stu says, but then I'd need to think about turning it on before two consecutive showers could be taken, or wonder how much hot water is left after washing dishes. Just like in my house - I don't turn off the heater when I go to work for the day, but if I'll be away on vacation for a week I will.
 
Last edited:
Nov 16, 2012
1,037
Catalina 310, 2000, #31 31 Santa Cruz
Rob, there is no reason to do that. It only takes 15-30 minutes to heat the water. Then turn the AC OFF. No need to keep running power to already hot water, plus you're depending on a thermostat to keep it from overheating. In my new neck of the woods, it takes 30-40 minutes to heat the water 'cuz our ocean here is 47F, cooler than your 57F. I can be patient and wait that long...:)

If you get into the habit of using the hot water faucet even when your heater is off, you'll keep water moving thru the ehater and avoid any stagnation.
It seemed to me that it took longer than that to warm up when first turned on, but I’ll admit I’ve never checked carefully. I will do that, and if it’s quick enough turn it off when we leave the boat.
 
Jan 7, 2011
4,723
Oday 322 East Chicago, IN
I don’t leave mine on, because I am at the marina mostly on the weekend. I may get out for a sail Wednesday nights after work, but don’t really need hot water.

I will usually turn the breaker on if I am going to be at the dock for a while working.

Greg
 
Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
We turn the hot water heater off when we leave the boat. No need to waste electricity keeping water hot for a week when we are not on the boat. It takes about 30 minutes to heat the tank once it is turned on. We'll turn it on when there is a need for HW, which while we're at the dock not that often. We have a 6 gallon Raritan.

Heating the water by running the engine will be even faster and hotter than with shore power. The heat exchanger is more efficient at transferring heat than an electric element. The water will also be at 160° or the engine's operating temperature, which ever is higher, and will stay hot for a long time, like 12-15 hours.

Besides wasting electricity, if the tank should empty while the power is on, it will burn out the expensive electric heating element.