Water Tanks from the

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Water Tanks

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I have a V-42 aft cockpit, hull 166. Water tanks are leaking very, very slightly, less than 1/2 gal per day total. Leaks appear to be on seams that are rusting slightly. Viewing inside through access panels shows rusting on seams with other sections of tank in great shape.

Has anyone had the same problem and what was solution? Remove and replace or repair. Any insight would be very helpful. Thanks.

Van Anderson October 2000


Scrub the water tank and clean and dry. If possible wipe down the seams with acetone, mix a quanity of marineTex and apply to all seams. Seal all water tank outlets and install a schrader valve in the vent connection. While the marineTex is still wet, reinstall the cleanout plate and pressurize the tank to 3-4lbs and leave set for about 8 hrs. Then vent tank and restore all fittings. This should force the marineTex into the holes in the seams.
Tom Cagney October 2000



Rockie and I talked with Jesse Frederick and Jim Kavle of Imagine Yachts in Annapolis and they suggest getting a company that will build a bladder tank to fit your tank and then cut a larger hole in top. Clean out the tank and install the bladder and fittings, manufacturing a larger access plate for the top. However if Tom Cagney is right, his approach sounds almost too good to be true, and should certainly tried first. Tom, have you been there before?

Bill Truxall October 2000



I had leaks in the water tank on my 37 and used this method to repair the seams. One thing I did not mention to Van, I used plastic corner edging that is sold in wallpaper stores to hold the marinetex and pressed it into the corners. It has held for several years and is worth a try.

Tom Cagney October 2000


One thing to keep in mind....Stainless Steel is a strange animal. It has the most galvanically reactive metals all mixed into one alloy, yet it doesn't rust (too much)... One problem though, is maintaining the balance of metals during the welding process. If you look around at all sorts of welded stainless, you'll see more corrosion in the welds because the welded area metallurgy was not well controlled and the weld is actually something other than stainless.... I noticed this happening on a welded stainless water lift on my previous boat... The welds failed, displaying pinhole leaks... Stainless tends to corrode more in a moist, oxygen-starved environment.... hence happening in the tank welds, which are submerged in water.... this is one reason I won't put those pretty, tight anti chafe covers on my shrouds, and why chainplates and lifelines fail....moist, oxygen starved stainless..
Matt Helms October 2000


I talked to a guy in San Diego today that repairs tanks, fuel mostly but water as well. He is aware of two tank coatings, Ceram-Kote and Plastisol (sp). They are both 2-part coatings with great flexibility. I will know more next week and will send update then but for now . .
1) Ceram-Kote requires a #80 anchor surface. This would require sandblasting to get to every nook and cranny. Any surfaces missed in preparation would be a problem.
2) Plastisol (sp) can be applied to clean dry surface. No sanding or other difficult prep necessary.
I also asked him about Tom Cagney's Marine-tex under pressure method and he agreed that would also work.
Will meet him next week and update when I know more. Thanks for the comments and help.
Van Anderson October 2000


There is also an outfit in Rome, NY, called Microseal which produces a sealer material which is used to seal porous castings. In experiments which I did, I found that it would seal tanks with holes as large as 1/16 inch though it is most effective for sealing smaller leaks. Sorry, I don't have their number here but one can get the number from information.
Earl Potter October 2000


There are very common strains of molds & mildews (especially aspergillis) that are extremely toxic and pathogenic. (Harvey can probably fill in the neuro-toxicity potential). There are many documented/reported cases (especially in cities) by public health agencies, etc. of extreme toxicity gained by simply 'touching' them or especially inspiring their spores. These are the black slime molds/mildews that grow on wet basement walls ..... and in the 'dark' spaces on boats. Not all are toxic, most may be so - at least to some minor degree, etc.
Anyway.....I KNOW they grow prolifically in boats !!!! I don't want to drink them, I dont want to wash my dishes with them, I dont want to rinse my toothbrush with them, etc. The problem occurs when you draw-down your water supply from the tank. These species grow best in the warm & dark locations (like exactly where your tank vent is always hidden). ..... and the tank vent is OPEN to atmosphere.
Scenario: You have a minor to occasional 'mildew' problem on your boat (everyone has one). You have no idea where the tank 'vent' is; or, never knew you had one. .. it's hidden under or behind some panel, .... is most probably in the dark (and with high humidty). --- mold/mildew grows all over the hidden space. You draw-down some water, air in-rushes to the tank, ... the mold/mildew spores are now in your tank. Aspergillis, etc. is now growing throughout your entire water system (it’s a matter of degree - but it IS there).
Without a 'bacteriological aerosol blocking filter', etc., the spores from these and other organisms are easily drawn into the vent and hence into the tank (the entry point is probably in your boat's mildew incubator!!!!) Once in the vent tube, they begin to actively grow down the walls of the humid, dark tubing and eventually begin to grow on the humid dark walls of the tanks themselves (using the metal and plastic etc. components as their nutrient source). A cursory visual inspection will show (I never saw a boat's tank vent without this infection) what looks like 'algae' growing on the inside of tubing. .... and, if you find it there in the vent, most certainly it has also infected the entire piping and tankage system. Sometimes in grossly infected systems you can see the "algae" (discoloration) growing on the insides of the clear tubing that connect the various components - yum!
The easy prevention remedy is to place a 'bacteriological aerosol retentive' filter in the line (after you 'sanitize' the whole system) to prevent aspiration of the spores into the system during draw-down. Encapsulated teflonic (bio-retention rated) membranes (about 50-70 mm diameter, encased in a plastic capsule --- ie.: Whatman #2101 @ $5.00 ea., etc.) are the current retention membrane of choice. The 'economical' alternative is to simply take a large to moderate sized 'wad' of dry sterile gauze /sterile cotton .... and liberally "bandage" the open end of the tube with it. Keep it dry and change every 6 months or so. Once you protect the 'vent' you wont have these 'critters' growing down into the tank. Once an infection begins, it accelerates and promotes the growth of other organisms until you have a fermenting 'brew' going on in the tankage. As each of these 'critters' sucessively infect and eventually die, they become the nutrient source for others, etc. etc. until all you are left with is a stagnant gooey mess instead of potable water. My claim (for the USA which has 'mostly' safe drinking water) is that THE PRIMARY source of tankage infection is the ***vent*** - totally abandoned, in a dark warm place, .... totally unprotected and totally OPEN to the atmosphere. Would you drink out of a water cooler that had a tube that was open to the atmosphere... for weeks, for months, years even... and NEVER cleaned!!!!??? No you wouldn't, ....not twice.
....... now consider then airborne bacteria, viruses, etc. etc. etc. etc. .....
The technical basis of all the above is a fairly simplistic methodology to lessen the infection potential of a "draw-down" (open to atmosphere) water tankage system; and, is based on the similar standard practice as is REQUIRED in a pharmaceutical, biological, food, or beverage plant's water system.
BTW - I know of several folks who consistently and repeatedly developed "respiratory problems"/asthma-like symptoms after several days on their boats... my recommendation was a thorough "killing of the" mold (includes tankage sanitization) and a "safe" removal process ( + tank vent ) ....
Result: no more 'respiratory problems'.
.... and just when you thought everything was fine and dandy, some smart-ass tells you your boat's water is probably poisoned ...... it just never ends. :-(
regards, Rich Hampel November 2000


Without going into a long winded dissertation of sanitization of onboard potable water systems, once you have a contamination, the only surefire method is to disassemble, mechanically clean & scrub, then shock sanitize the system to prevent reinfection. Any discolored hose should be replaced as discoloration means that fungal, etc. species have penetrated into the plastic! Commercial, industrial, municipal, etc. shock sanitization is by adding enough Clorox (there are other methods) to get up to 10 parts per million of free chlorine, let the chlorine digest (a few days) to stun/kill the growth, scrub, and reshock with Chlorine, drain, rinse, drain, rinse, drain, rinse, etc. (You can’t do this if your tank is aluminum - as chlorine will react with the aluminum). If you dont remove the "dead bodies" by mechanical scrubbing, etc, those 'dead bodies' become a nutrient source for subsequent infections.
The 'maintenance' dosage of Chlorine is 1 parts per million (sufficient enough so that you can "just barely perceive a faint chlorine smell" with your nose).
The most probable entry point for most infection is the tank VENT which draws in spores, etc. every time you turn of the faucet and draw down the tank. My usual (strong) recommendation after tank cleaning and sanitization is to place a hydrophobic bacterial retentive filter on the vent exit, or more cheaply - taping a large "wad" of dry sterile bandage gauze over the vent and keep it dry, change yearly. Typical infections are usually molds and mildews including Aspergillis, etc. of which some species can be toxic (Its that black stuff that grows in the dark spaces of your boat.) If you get continual reinfections..... change out and replace the entire vent line, etc. and add the gauze or blocking filter.
Keeping a 1 part per million 'maintenance' level of Chlorine (dont calculate the numbers, use your nose) requires that you dont use a carbon packed filter in the system as the carbon will remove the Chlorine from the WHOLE system. (Incidentally, the carbon pack filter will become a breeding/nutrient site for other microorganisms - I'd never ever have one on my boat) Shock sanitize with 4 oz. of Chlorox per 10 gal. Maintain with 0.4 oz. of Chlorox per 10 gal. ... + add more to be able to notice the 'very faint smell'. (Commercially available Chlorox is a 5% solution.)
hope this helps, Rich Hampel July 2001


Yes, just take a large fist-sized 'wad', cover the end of tube and tape it in place, leaving the maximum of exposed area possible. Better, ... you can take absorbing cotton (loose) and make a 'sandwich' with the gauze as a covering to hold the cotton in place. The gauzed end should be located high enough so that it cannot become wetted by water from the tank.
Rich Hampel July 2001


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