A Paint-In Tank Liner for Heat Storage Tanks

This is Gary Reif's post on the Yahoo Simply Solar group describing the solar heated water storage tank that he built using a paint in, flexible, polyurethane tank lining product call PermaFlex.

The PermaFlex is said to remain flexible for "life" and to be good up to 250F.

This looks like a promising way to line tanks, but bear in mind that (as far as I know) it has not been used extensively solar heat storage tanks. Also, bear in mind that Gary took great care when building the tank to avoid gaps and to build stiff walls that will deflect very little -- this may be an important factor in having success with this paint in liner.

If you have experience with using PermaFlex as a liner for a heated water tank, please let me know...

Thanks very much to Gary for providing this material!!

For other ways to do solar heat storage tanks..

From Gary:

Building the Tank Shell

I took 3/4" sturdi floor which is an extra strong tongue and groove plywood for floor construction and laminated it with 1/2"
plywood to get 1 1/4 thick sheets which make up the tank. 4 vertical inside corners are just 2x4's butted in corners for strength. Floor is the 3/4 sturdi floor on a 2 x 4 frame wide side laying down with about 16" spacing squared since it's a lot of weight. I used lots and lots of 2x4 around outside of tank since this 900-gallon tank is holding back 7500 lbs of water.

Applying the PermaFlex Lining

Four coats of permaflex on the inside of the plywood, which is easy to do but stinks and strong fumes since you are in the paint painting it on. It's a rubber polyurethane.

PermaFlex lined tank with heat exchanger.	Routing pipes over the top of the tank sides avoids penetrations.

Info from their website http://www.sanitred.com/permaqualities.htm

SANI-TRED PermaFlex is a single component (1 part), liquid rubber "ULTRA ADHESIVE" paint-like coating. After cure, there is little resemblance to paint. PermaFlex is a paint replacement product, self-priming, easy to use, easy to apply and cures reliably even in extremely cold temperatures. A good analogy of PermaFlex is "a roll on, seamless, flexible liner that bonds permanently to the surface and beneath the surface". PermaFlex bonds permanently to most all standard building materials.

Things I would do different with the coating

I assumed it would fill gapes even though the website says it doesn't and they offer a product that does, so after I applied 1 coat I had to order the filler product which was a pain to work with. To do it again I would on the bare wood use a product like PL400 to fill all cracks/ seams/ screw heads and would put a nice radiused bead in corners then coarse sand it all to get adhesion to PL400. Doing this would make applying the permaflex much easier and would have a better tank with less chances of a leak.

Hope this helps.

Gary Reif

Gary will answer email questions at: greif123456789 AT yahoo DOT com (replace AT with @ and DOT with a period)

Gary November 21, 2010