Potable water tank construction

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Scott T-Bird

Scott T-Bird

.
Oct 26, 2008
6,432
Catalina 320 Barnegat, NJ
Hi all,

I pulled out the 14 gallon aluminum water tank that resided below the port salon seat and decided to replace it and add a second water tank to be close to the same shape under the stbd seat. It will be less length so the total capacity will be 26 gallons (14 + 12). The original tank had to have been a custom design and I searched all the tank manufacturers that I could find and did not find any that have the similar shape (triangular), cross sectional dimension and length that I want.

So the tanks will need to be built. My economic options appear to be:

3/8" polypropylene from Dura-Weld price proposal totals $870 for the 2 tanks.
1/8" 5052 Aluminum from a local manufacturer priced at $672.
Stainless steel from the same local manufacturer priced at $1,243.

I don't know how important the desire for potable water is since we currently have no need for it, but hope to have a future need for it. The aluminum is supposedly NOT suitable for potable water. I've heard mixed opinions on the plastic, depending on the plastic. If the water smells, that isn't good, even if we don't need potable water.

Is the price differential worth it for the SS?
 
Bill Roosa

Bill Roosa

.
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Building tanks from fiberglass is not that hard. If you still have the old tank you can use it as a model. make flat fiberglass panels to near the size, cut them to the exact (ish) size. Then fiberglass the panels together with fiberglass tape. Glass in some hold downs and the vent and supply line and install. Gotta be cheaper than $672 and you develop some fiberglassing skill
 
MrBill_FLL

MrBill_FLL

.
May 4, 2005
4,062
Macgregor 26d Ft Lauderdale, Fl
1+ build it with epoxy fiberglass. door skin or 1/8" ply makes good forms.
 
Ross

Ross

.
Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Nicely waxed "formica" is excellent for making fiberglass sheets. The first layer should be chopped strand mat and vinylester resin will make the work go faster.
 
Bill Roosa

Bill Roosa

.
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Figerglass does not stick to saran rap and it takes a shape much better if you need that feature. I've use it to make dagger board wells shaped exactly like the dagger board. Works great and the price is right.
 
RichH

RichH

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Feb 14, 2005
4,773
Tayana 37 cutter; I20/M20 SCOWS Worton Creek, MD
Whatever you do, DO NOT make potable water tanks from either standard epoxy or standard styrene/polyester based resins .... unless they are guaranteed SAFE vs. potable water. Usually such guarantees are 'wetted surface area' dependent - maximum volume per minimum surface area exposure.

There are some epoxides available in a low amine content that is suitable for contact with potable water and are NSF certified for use with potable water ... NSP-120 www.epoxyproducts.com ... the contact surface area per volume has to be maximized. You can even 'rebuild' your current tank with epoxy/fiberglass and use such as the final coating / laminate layer that comes in contact with your drinking water. Simply cut a BIG hole in the top of your current tank, build a FRG 'liner' including the use of the PROPER low amine, NSF approved epoxide for the 'wetted contact' final layer. Quite easy to 'sister' a large flat plate + studs for the closure of the rebuilt tank.

Ignore such potable requirements per NSF etc. standards, and expect to grow little purple bumps on vital internal organs and brain tissue, sometimes BIG purple 'bumps and lumps'. The chemical fragments and 'monomers' that continually leach out of improper resins in drinking water can do accumulated severe harm to your vital organs.

LOW amine content, National Sanitation Foundation - NSF certified for usage with potable water - ONLY. ;-)
 
Scott T-Bird

Scott T-Bird

.
Oct 26, 2008
6,432
Catalina 320 Barnegat, NJ
Hmmmm, thanks for the thoughts, but I don't want a fiberglass project. I am basically looking for the merits of SS over plastic. I am sure that I am ruling out aluminum (including the price was just for context), but I am not sure that the expense of SS over plastic is necessary. But if I am going to fabricate the tanks, I want to do it just once and get exactly what I want.

I know that creating a mold for roto-molding plastic is too costly for a one-off, so I am essentially wondering about the suitability of welded plastic such as Dura Weld or Triple M.

MS, I will certainly send my specs to Triple M if I decide that plastic is suitable. I wouldn't expect their price to be much different than Dura Weld though, just for relative comparison between SS and plastic. The price for metal fabricating is based on a local outfit and they are fabricating an aluminum fuel tank for me (believe it or not, I could not find a ready-made plastic tank in the exact size that I want to fit my compartment).
 
Bill Roosa

Bill Roosa

.
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
You can also fabricate Dura weld if you can find the raw stock
yea, I know, Bill is always with the DIY solutions.
Get a BIG electric soldering GUN (not an iron)

On the fiberglass project (in case there are others considering it) I've found it much easier to make a big flat sheet of fiberglass of the correct thickness and then cut out the pieces rather than make the individual pieces and the cut them to the exact size. almost like working with wood at that point.
FWIW
 
Bill Roosa

Bill Roosa

.
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
I would note that Rich's comment on toxicity is correct and you can overcome it with the application of a good internal coating like plastic sheeting, trash bags, saran wrap (several layers) etc.
 
P

Pat

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Jun 7, 2004
1,250
Oday 272LE Ninnescah Yacht Club, Wichita, Ks.
what about the flexible tanks? My water tank has a crack the length of the 30 gal. tank, at the top that only leaks when the boat heels over...so I do not fill the tank....filling a tank should not be a variable that is dependent on the day's weather....I've tried to fill the crack to no avail. Perhaps I am using the wrong product....but I've been thinking of the flexible tanks that are available. Any thoughts on those? we have water available at all the slips at no charge so the size of the flexible tank doesn't seem too important. Pat
 
C

cabritapointe

.
Apr 21, 2013
1
Sabre 42 Annapolis
Why not use flexible water tanks instead...perhaps Nauta ta?

Scott T-Bird said:
Hi all,

I pulled out the 14 gallon aluminum water tank that resided below the port salon seat and decided to replace it and add a second water tank to be close to the same shape under the stbd seat. It will be less length so the total capacity will be 26 gallons (14 + 12). The original tank had to have been a custom design and I searched all the tank manufacturers that I could find and did not find any that have the similar shape (triangular), cross sectional dimension and length that I want.

So the tanks will need to be built. My economic options appear to be:

3/8" polypropylene from Dura-Weld price proposal totals $870 for the 2 tanks.
1/8" 5052 Aluminum from a local manufacturer priced at $672.
Stainless steel from the same local manufacturer priced at $1,243.

I don't know how important the desire for potable water is since we currently have no need for it, but hope to have a future need for it. The aluminum is supposedly NOT suitable for potable water. I've heard mixed opinions on the plastic, depending on the plastic. If the water smells, that isn't good, even if we don't need potable water.

Is the price differential worth it for the SS?
Click to expand
I use flexible Nauta tanks for extra capacity for water and diesel...
 
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