I need to replace the fresh water tank, It is in the floor in the aft state room between the beds.

Does anyone have any pictures of the floor removed in that area showing the tank?

I have a place to get a poly tank but my concern is getting the old one out. 

I can see one end at the stern but it looks like the other end may run under the bath tub, cutting the floor does not look to bad but if the tank is fastened somehow under the bath tub it could get ugly!

I'm prepared to have to cut it in half to get it out, but I want to be sure i can get the part out under the tub.

Piping looks pretty straight forward. And I will probably go with around a 120 gallon in lieu of the existing 200 gallon galvanized existing tank. 

Any information would be appreciated.

Thank you 


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Hi John

I also own a 1979 45 Commander, i had a fresh water leak in the aft stateroom under one of the fuel tanks which I thought was coming from the fresh water tank. I opened the floor to discover the water source was coming from the port shaft strut bolts. I ended up undoing the port side bed and removing the fuel tank to access and successfully repair the hull. During my investigation I looked at the water tank thinking I might have to remove the tank, it did not appear to go much further than the clothes closet but I am not 100% positive as my repair area was redirected. I would appreciate hearing back from you in due course how you end up fixing the problem and how far the rank runs. Good luck

Thanks Steve, 

I don't have any leaks "yet" but I do have a tank full of rust. I have a whole house filter coming off the tank and it will clog after 4-5 gallons of water are used.

If I let it sit for a half a day after we were under way it is not to bad but it's time to replace it as we are using the boat more after a few years or ironing out the bugs.

I will document the process and post when I proceed. Should start around mid April when we unwrap her.



Hi John
A suggestion when installing your water tank

In the engine room where the pipe from the fresh water thank enters the engine compartment, I added a bypass valve with a faucet. When the valve is turned one direction then the fresh water flows towards the fresh water pump. Turned the other direction and open the faucet, the water gravity flows into the bilge. In the fall when on the hard I remove the bottom hull plug and drain the tank without using the electrical pump. Alternatively the bilge pumps are quicker and more efficient.

In early spring I fill the water tank and add two cups of Clorox and let it stand a day. Then I drain the tank via the faucet and thereafter flush it several times with fresh water. Tank is cleaned but no Clorox in pipes. Also bilge gets pretty clean

Water filters:

I also added an «under the sink type » cheap type filter 30 micron. This filter captures stuff from the tank before hitting the pump. When the filter starts to look a little greenish I install a new cheap filter.$10. -then I added a more sophisticated filter with separate lines going to separate (new install) faucets in the galley and heads to supply drinking only water. This filter has 5 micron filters and is good for about 800 gallons and cost $100+ So you DON'T want to use it for dishes or showering.

We travel long trips and some remote marinas have water wells and this eliminates sulphur smell/taste.

Finally, (and you might think I am nuts) I also added yet another dedicated faucet in the galley connected to a wash down pump installed in the v-birth (I used the existing thru hull for the toilet) thus drawing water from under the boat. When cruising in relatively clean waters, then we use this faucet to wash our hands or pre-rinse dishes and after washing then a quick rinse with tank water. This method has greatly extended my need to replenish fresh water.

Good luck and fell free to contact me if needed



Should read DON’T

« So you don’t want to use it for dishes or showering. »


I like the draining idea, I will work that into the re-plumbing for the new tank.

I plan on a poly tank and I can fill the tank from the dock by opening a valve in the engine room. I have a filter on the dock water feed too. hopefully it keeps the new tank as clean as possible.

I also do the Clorox sit and rinse but my major problem is the rust.

Being in salt water I wont be using it for any wash downs.

Two days at anchor would be the most, so I am planning my fresh water usage around that with a day or so buffer. 

I would like to put the biggest tank I can back in but the round bottom flat top existing tank is going to get replaced with a long rectangle tank that will fit in the available space, estimating 120 - 150 gallons.

Won't know until I open up the floor.

Appreciate all the information.



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