Fiberglass tank refit - should I cut it open?

[leveche420]

Hi,

I took the water tank">fresh water tank out of the boat. I am considering reconditioning it since custom made tanks seem to cost a lot. The interior of the tank (gelcoat?) has blisters and it's chipping off as you can see in the attached pictures. It will have to be sanded down and re-coated with some epoxy coat that is food grade and safe for fresh water. My question is... Should I try to sand and recoat through the inspection ports? Or should I cut up the upper side, work the interior and then fiberglass it back together?

Thanks!

[skipmac]

Inside of my tank looks just like that and I'm considering the same thing, cutting the top out to coat the inside with epoxy or doing nothing and just keeping the tank clean.

Very interested in hearing the recommendations.

[scherzoja]

I ran into the same problem. My two tanks are fiberglass, gelcoat on inside, built-in, two baffles, 50 gallons each. Many blisters, mold, and strong odor of fiberglass. Busted baffles that needed reattachment.

Cut them open fix the blisters, then paint with potable water epoxy.

I did this with the built-in fiberglass tanks. They are not integral to the hull, just built-in.

I also made some large access hatches

Potable water epoxy:
https://www.epoxyusa.com/coat_tar_p/ep34.htm

My water tank work on my Pearson 367:

Water Tank Access. (my ID on Pearson 365.com is p69)


My pictoral documentation of that work

Water Tanks-Cleaning and Fixing - LA Gallery

Water Tanks - New Custom Access Ports - LA Gallery

Good luck on the decision-making. That's often the most difficult part.

Skipmac. Your 424 tanks are probably just like mine with one tiny 6" inspection port on the after end of each tank.

[Matt Johnson]

Cut that top off! It will be very easy to reglass the tank top from the outside after you've done your work.

I had to grind and epoxy the inside of two integral aluminum tanks on my boat... it was horrible and the result is not perfect. I'm envious of how easy it will be for you once you have the tops off.

Matt

[coopec43]

I'd sand the inside through the inspection port if you can and if you can't then maybe you should add another port as potable water tanks should be cleaned regularly.

How often should water tanks be cleaned?
It is necessary to clean and disinfect your water holding tank(s) at least once a year or more often, if required. This is to remove algae (plant growth which produces bad tastes and odours), silt, and bacteria which may be harmful

I wouldn't use epoxy in a water tank as it is considered harmful

Epoxy in Water Tanks
Epoxy water tanks have been around for more than four decades, but it is notable that West does not recommend epoxy for drinking water tanks because of regulatory and safety issues. For an excellent perspective on the subject, I suggest you consult West’s online Epoxyworks article at epoxyworks.com/18/pdf/tanks.pdf. It includes advice as to the correct hardener ratio for a water-tank repair (Don Casey)


(I can't get that link to work but I think the Internet may be down. Try googling "Wood/epoxy composite tank guidelines - WEST SYSTEM Epoxy"
The article I read was that it was OK for professionals to cure the epoxy properly - heat/steam cleaning X3 etc etc but impossible for the amateur)


I coated my tanks with a water based bitumen (Crommelins) which is approved by the WHO for potable water.


Clive

[coopec43]

Fiberglass is not considered safe to store potable water unless it has been coated.

There is a lot on the Internet regarding styrene the potential threat to health.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC156662/


Clive

[Matt Johnson]

There are tons of potable water tank epoxies available. Just about every steel water tank is coated with one of those for municipal storage (water towers). We used Sherwin Williams water tank coat over a few coats of West System. But, if you read between the lines from West Systems literature, you'll see that while they haven't been approved for potable water (they haven't spent the capital on government testing) theirs doesn't leach after curing... If I remember correctly, it was a two week cure time.

Matt

[coopec43]

I found the West Systems article.

Epoxy Composite Tank Guidelines
By Patrick Ropp

https://epoxyworks.com/index.php/epo...%2C%27tanks%27


Why we don’t recommend building an epoxy composite tank for potable water

We have adopted the broad policy of not recommending epoxy for drinking water tanks because of regulatory and safety issues. The potential problems outweigh the benefits. To date, none of Gougeon Brothers’ epoxies meet FDA regulations or any other drinking water certified approval. The major long-term concern with any plastic water tank is extractives leaching out in the water. Off-ratio, poorly cured epoxy can release extractives, as noted above. In the fabrication of water tanks and food handling equipment, the successful use of epoxy requires thorough mixing and adequate elevated temperature post-cure to assure the maximum cross-linking and cure of the polymer. These process controls are not always possible with the home-built tank. Unfortunately, neither Gougeon Brothers, Inc. nor any certification agency can verify the level of quality control exercised in the fabrication of the tank.

Clive

[leveche420]

Originally Posted by funjohnson

Cut that top off! It will be very easy to reglass the tank top from the outside after you've done your work.

I had to grind and epoxy the inside of two integral aluminum tanks on my boat... it was horrible and the result is not perfect. I'm envious of how easy it will be for you once you have the tops off.

Matt

Thanks Matt!

Question... would you cut right around the perimeter (red line) or would you leave a lip (green line) to fiberglass on top of it when I put the top panel back in place?

The risk of cutting thru red line is that I may damage the bottom panel as I cut along. The downside of cutting through green line is that it will still be difficult to access that little corner in the interior.

[leveche420]

Originally Posted by coopec43

I'd sand the inside through the inspection port if you can and if you can't then maybe you should add another port as potable water tanks should be cleaned regularly.

How often should water tanks be cleaned?
It is necessary to clean and disinfect your water holding tank(s) at least once a year or more often, if required. This is to remove algae (plant growth which produces bad tastes and odours), silt, and bacteria which may be harmful

I wouldn't use epoxy in a water tank as it is considered harmful

Epoxy in Water Tanks
Epoxy water tanks have been around for more than four decades, but it is notable that West does not recommend epoxy for drinking water tanks because of regulatory and safety issues. For an excellent perspective on the subject, I suggest you consult West’s online Epoxyworks article at epoxyworks.com/18/pdf/tanks.pdf. It includes advice as to the correct hardener ratio for a water-tank repair (Don Casey)


(I can't get that link to work but I think the Internet may be down. Try googling "Wood/epoxy composite tank guidelines - WEST SYSTEM Epoxy"
The article I read was that it was OK for professionals to cure the epoxy properly - heat/steam cleaning X3 etc etc but impossible for the amateur)


I coated my tanks with a water based bitumen (Crommelins) which is approved by the WHO for potable water.


Clive

Thanks Clive!

I can reach with my hands pretty much everywhere inside the tank but is hard for me to see inside. Plus sanding and coating thru the inspection ports will be time consuming and I will never do a great job. I have to cut the top up but I cannot thing of a viable process to work the inside thru the inspection ports but I am still thinking, I havent made a final decision yet.

Regarding epoxy being harmful... I am clueless about these materials and coating products but I do see that some epoxy coating paints claim to be suitable for drinking water. One example is the one Scherzoja proposed: https://www.epoxyusa.com/coat_tar_p/ep34.htm

Are these companies just not telling all the truth? What am I missing?

[leveche420]

Originally Posted by coopec43

I'd sand the inside through the inspection port if you can and if you can't then maybe you should add another port as potable water tanks should be cleaned regularly.

How often should water tanks be cleaned?
It is necessary to clean and disinfect your water holding tank(s) at least once a year or more often, if required. This is to remove algae (plant growth which produces bad tastes and odours), silt, and bacteria which may be harmful

I wouldn't use epoxy in a water tank as it is considered harmful

Epoxy in Water Tanks
Epoxy water tanks have been around for more than four decades, but it is notable that West does not recommend epoxy for drinking water tanks because of regulatory and safety issues. For an excellent perspective on the subject, I suggest you consult West’s online Epoxyworks article at epoxyworks.com/18/pdf/tanks.pdf. It includes advice as to the correct hardener ratio for a water-tank repair (Don Casey)


(I can't get that link to work but I think the Internet may be down. Try googling "Wood/epoxy composite tank guidelines - WEST SYSTEM Epoxy"
The article I read was that it was OK for professionals to cure the epoxy properly - heat/steam cleaning X3 etc etc but impossible for the amateur)


I coated my tanks with a water based bitumen (Crommelins) which is approved by the WHO for potable water.


Clive

Is this the water based bitumen (Crommelins) product you used?:

Water Based Bitumen Paint: Waterproofing: Crommelin

[leveche420]

Representatives from International recommend this product:

Interline 850

https://www.international-marine.com...nterline-850-3

[Terra Nova]

Water tanks need to be thoroughly cleaned periodically. That's why cutting the tank apart and glassing it back together makes no sense at all. Better to install manhole clean-outs, make appropriate repairs, and coat using the WEST-recommended 207 special hardener.

[leveche420]

Originally Posted by leveche420

Representatives from International recommend this product:

Interline 850

https://www.international-marine.com...nterline-850-3

Here is another option for coating the interior of the water tank that I came across:

Tank Clad HS Epoxy

https://protective.sherwin-williams....3aproduct-6855

I was also considering Devoe 233H (eopxy paint) but it may not be suitable for drinking water.

[leveche420]

Originally Posted by Terra Nova

Water tanks need to be thoroughly cleaned periodically. That's why cutting the tank apart and glassing it back together makes no sense at all. Better to install manhole clean-outs, make appropriate repairs, and coat using the WEST-recommended 207 special hardener.

Through the existing inspection ports I could clean the tank if the interior coat was not damaged. Because it is damaged I need to sand and re-coat. I think sanding and coating the interior thru the inspection ports will be very challenging