Should I keep the water tank full or empty?

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Boater On Thames

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My boat has a 100 gallon fresh water tank. I leaned some saying online said should keep it always full to prevent corrosion. So I used to keep it full all the time. Then some people told me empty it while not in use for long periods, especially in winter. They said that is because worry it will freezing.

Which choice is the better option? Keep it full or empty? What will you do?

Thanks.
 
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Our first boat had had a replacement tank before it was 3 years old because it froze and split while out on the hard in Plymouth. It was close to the outside of the boat. Current one is under our bed in the bottom of the boat and kept in the water all year round so we don't worry about it.
 
I empty my tanks in the winter to save the pumps freezing, etc. In the summer if the boat hasn't been used for a few weeks I try to empty the tanks before refilling so that I have fresh tap water on board. The water is drunk straight from the tanks, sometimes via a general ecology filter if I remember.
 
Your last thread you didnt particularly want anti freeze in your engines because your temps never got that low and now you are worried that your water tanks might freeze. So which is it?

If you freeze empty the tanks and drain individual items such a calorifier, toilet, shower heads, grey water sumps etc. Come summer replace water evry two weeks or so. Fresh from the faucet it will already have chorine etc in it that will keep bugs etc at bay for a short while. If you cant do every two weeks a tablet of Milton or two will replenish that which has gassed off. Do a tank sanitization of winterization and flush through to get rid of any bugs and algae growth
 
Thank you mate. I asked because I continue doing service and lots other maintenance works on the boat and now working on the water system. I never had freezing problem as my boat always on the water and here in south of England is not clod engou. I was thinking keep the tank full all the time until a BSS exmamer told me empty it for better protection in the winter 2018.

So I think I am going to flush it and add a chorine tablet in it from now.

Thanks.
 
Hadenough said:
If the calorifier is installed properly it can be 90% drained via the over pressure valve. I do this and suck the rest out with a wet vac.
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Being a heating engineer I wouldn’t recommend using the PRV to empty your calorifier. These can become leaky after a while, especially if a small piece of scale or dirt gets on the seating. It will then just drip and drip into your bilge. At worst it could just give way when the pressure builds when water is heated.
 
Tarlach Too said:
Being a heating engineer I wouldn’t recommend using the PRV to empty your calorifier. These can become leaky after a while, especially if a small piece of scale or dirt gets on the seating. It will then just drip and drip into your bilge. At worst it could just give way when the pressure builds when water is heated.
Click to expand...
The better PRV valves also incorporate a drain cock, although when I wanted to replace mine, which had, I couldn't source one for a realistic price. I installed a tee piece, so that the PRV was on one branch, and a drain cock on the other.
 
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