The problem was that our fiberglass fresh water tank (located in the keel under the cockpit sole, about 100 gallons volume) was blistered and had spider cracks. It was still sound, but the water quality was poor due to the styrene leaching into the water from the venting blisters.<\/p>\n
We figured we had the following repair options:<\/p>\n
A. Remove the tank and install a new one. The problem with this approach is made clear by an email from Jeremy Lines: The water tank is 4′ x 3′ x 2′-1″ so will not go through the doorway. It is also partly structural where it is matted in along the sides and at the forward end.<\/p>\n
B. Cut out the top of the tank and install new bladder tanks inside. Either a couple stock size bladders could be inserted, or a custom bladder could be made.\u00a0 The custom bladder supplier<\/a> I talked to reckoned the bladder would only last about 5 years, and would cost about $750. So this is a costly option with a limited lifetime. (Note added later: We eventually did this option after our first attempt described below failed, but the idea of a bladder failed as well. The custom-made bladder was well-built to our specs, but the odd shape of the tank made it really hard to get it to lay inside perfectly, so there were always wrinkles and folds that we hard to clean. And it made the water taste and smell like plastic – so we abandoned it after less than a season of use. Now back to the saga as originally written.)<\/p>\n C. Cut out the top of the tank, and install a polyethylene rigid tank. This seemed reasonable, but again we have problems getting a tank through the companionway door, so would likely lose some volume. Also, tanks of this size are pretty pricey, and shipping is not cheap either.<\/p>\n D. Cut out the top of the tank, and do surface repairs. This is the option we decided to use. But then the next question was, repair with what? Epoxy coating is an option, but the blisters underneath would probably continue to vent, and this brittle epoxy coating would fail. (Others had reported this problem with epoxy paint repairs). We needed a flexible coating, sort of a paint-on bladder approach.<\/p>\n We finally settled on using Sanitred<\/a> materials called Permaflex and LRB, which are rubber-based coatings. They make some wild claims about this miracle material, so we decided to have a go.<\/p>\n ****Update May 2011 – This approach is a terrible failure. We do not recommend using Sanitred to coat the tank because it continuously leaches oil into the water. Sanitred swears the oil stops being produced, but after leaving the tank for 8 months overwinter, there was at least 1\/2 cup of oil in the tank – it was like sludge. The surface has also gone yellow, and the blisters from the fiberglass are causing the Sanitred materials to blister up too. In some cases, the Sanitred has enough elasticity to handle the venting fiberglass blisters – in other cases the Sanitred layers have burst. The end result is a tank that contains oily, smelly water. YUCK! ****<\/p>\n For those who want to know about this failure, here’s what we did:<\/p>\n 1. Let the tank air dry for about a week. Goal was to learn if the blisters would continue to vent brown goo. They didn\u2019t seem to.<\/p>\n 2. Use a jigsaw to cut off the top of the tank. Save this lid, and in all the coating steps listed below, make sure its inside gets coated too, as this lid will be reinstalled at the end. (To be honest, we didn\u2019t do this as step 2 \u2013 we tried to do everything from the portholes first. But after many nasty bruises, we cut off the top because reaching all the corners was just too hard with the top in place. We should have done this step at this point, so I report it here.)<\/p>\n 3. Hand sand the surfaces. This was tough work but only took a few hours. We did not try to do any blister repair. We just wanted to roughen the surface to get better adhesion for the Permaflex.<\/p>\n 4. Wipe down the tank with acetone to ensure the surface is clean.<\/p>\n 5. Mix Permaflex according to directions, and paint it onto all surfaces. This stuff is thick, so hard to spread.\u00a0 **See note below this list about what we should have done **<\/p>\n 6. Wait a few hours and then mix more Permaflex and paint on second coat.<\/p>\n 7. At this point, we went home for the night in hopes that the oil film Sanitred warns about would not form in the cool evening temperatures. Bad decision. After 8 hours, there was an oily film on the Permaflex, so we needed to wipe the surface down with acetone before we could start again. Nasty. If these steps are followed, start on the next step as soon as the second coat of Permaflex\u00a0is\u00a0applied (while\u00a0still wet)\u00a0because the next step takes a long time and the materials will reportedly adhere even if the bottom coat is not fully cured.<\/p>\n 8. Make a mixture of LRB\/TAV with no water as catalyst because TAV is a catalyst. This makes a toothpaste like mixture that can be pressed into all corners. This was very hard and very messy. The LRB\/TAV mixture is light blue in color, and when we were done, there was light blue blotches all over from the slop that occurred while trying to reach the corners.<\/p>\n 9. Mix LRB with water as catalyst, per the directions. Apply a coat, only to find out that the material is off-white yet translucent so the blue blotches show everywhere. It looked terrible and will make it very hard to tell if the tank is clean later in life.<\/p>\n 10. With the approval of the helpful support staff at Sanitred, we decided to apply another coat of the opaque Permaflex to try to cover the blue blotches of the LRB\/TAV mixture. Since the Permflex creeps so much prior to curing, it was hard to get sufficient coverage on the large blobs of LRB\/TAV mixture, so the blue color still shows through somewhat. BTW, we had to clean the oil off the walls again prior to this step. Frustration is pretty high at this point.<\/p>\n 11. Apply a final coat of LRB +water-as-catalyst mixture.<\/p>\n 12. Wait for it to cure and then wash off the oily surface with soap and water, again and again and again. The oil keeps coming back, though the folks at Sanitred insist it stops forming after full cure (about 24 hours).\u00a0 They say we are not doing a sufficient job of getting the oil removed, instead we are just smearing it around. Not clear who is right. We are using cold water and soap to clean tank, and perhaps warm water as they suggest is required but getting\u00a0several gallons of warm water into the tank is not easy because we’d have to heat it all on the stove.<\/p>\n 13. Time to reinstall the lid. We made some tabs out of Aluminum barstock that are bolted between the lid and tank to hold it in place. We then used 3M 5200 to seal the gap. This was not hard to do, and it was definitely worth cutting the lid off the tank to do the work.<\/p>\n **Note: If we were to do this again, we would have applied the Sanitred coatings in this order: 1) LRB\/TAV mixture into corners; 2) \u00a0base coat Permaflex; 3) second coat Permaflex; 4) top coat LRB. This would hide the blue colored LRB\/TAV mixture well and achieve the goal of a rugged impermeable yet flexible coating. And we would do all coats in one day so there was not chance for the oily film to appear between coats.<\/p>\n The Sanitred approach seems to have sealed the tank and the coats are well adhered from the start. I\u2019ll periodically provide status to indicate how this repair is going. The repair was made in late June 2010.<\/p>\n Status August 2010<\/em>: A few of the fiberglass blisters are venting under the Sanitred coatings as evident by the bubbles with brown goo under the Sanitred coatings. The Sanitred materials are holding up so the styrene goo is not making it into our water. Because the oil film that forms on the cured Sanitred products continues to plague us, we are not able to drink this water directly. It has an unpleasant smell too, just like the Sanitred smells while applying it. The oil sheen on the surface is less each time we wash it out, maybe we\u2019ll get rid of it all eventually. We are using about 1.5 Tbspn of bleach per 100 gallons of water to preserve water quality. The water is definitely usable for washing, but we are carrying drinking water separately.<\/p>\n Status May 2011<\/em>: As I wrote higher in this post, we do not recommend the Sanitred approach. The surface never stops leaching oil, so the water in the tank is polluted and smells strongly of Sanitred materials. Cleaning the tank and the lines is a real chore.\u00a0We found that\u00a0hot water and dish soap doesn’t clear the oil away, as the Sanitred documentation says it will.\u00a0 Though their website says “most solvents are OK” the printed documentation provided with the product says not to use alcohol. Eight months after application, we forgot about that ‘no alcohol’ warning\u00a0– and rubbed it down with alcohol. It’s did not change the problem or affect the surface as far as we could tell, but the use of alcohol\u00a0meant that the manager as Sanitred blamed the entire failure on its use – despite the fact that\u00a0we only used it AFTER the problem existed for\u00a0about 8-9\u00a0months.\u00a0\u00a0We’re at wits end with this, and have a nasty water tank problem on our hands. We bought a custom bladder so we could keep cruising while we sort out what to do with this problem.<\/p>\n Status May 2012<\/em>: After pulling out our plastic bladder for winter storage, and leaving the sanitred-coated tank exposed to air over the winter, we’ve discovered it has FINALLY stopped leaching oil. Maybe if finally cured? Who knows. We cleaned it with soap and water, and refilled it for use at the dock. All is OK now, and the water no longer reeks of Sanitred smells (though we wouldn’t dare drink it). So if you can apply this product and afford to wait for a couple years if something goes amiss – maybe it will eventually meet your needs for a non-potable water supply.<\/p>\n Status Spring 2013<\/em>: The Sanitred continues to be a problem. In frustration, we scraped all the Sanitred out of the tank, using brute force. Some of it came out in sheets, other parts were better bonded to the surface so it had to be scraped off with a putty knife, which did some damage to the gel coat. But it’s gone now – good riddance. \u00a0It was a mistake to be worried about the venting blisters in the first place. To resolve the problems with any styrene in the water, we installed an inline charcoal and particulate filter in the fresh water supply line. We chose the\u00a0Omnipure K5522-BB Carbon Block Water Filter<\/a> because it works well at the lower pressures of our house water system (that is, lower pressure in comparison to a house water supply pressure).<\/p>\n Status Fall\u00a02015<\/em>: We continue to use the Omnipure filter setup, and keep the tank clean. We’re happy with this solution – the water tastes good. It’s not obvious that the blisters are still venting – maybe we just keep the tank clean enough during our 3-4 month cruising season<\/p>\n\n\t\t