Is EPDM for tank liner a catch-22?

[NHFarmer]

Looks interesting,any ideas on cost and is it a DIY project?Keep us posted

 

[Fred61]

Looks interesting,any ideas on cost and is it a DIY project?Keep us posted

It is a DIY project. Of course it will be some time before we know whether it works or not (hopefully). I was in the adhesives and coatings buisness up until 1999 and have a lot of faith in the chemistry. What I did is cut one end of a 500 gallon fuel oil tank and, at present, am preparing the surface to accept the epoxy layer. I will be using the tappings for probe wells, and return water to my flat plate HX. The guy I spoke with at the supply house felt that poly urea (like some bedliners, not Rhino and Bullhide) would work because the operating temp. is about 230* but I decided to go for the epoxy, which has a working temp. almost 100* higher for that extra margin of safety. It isn't cheap. About $250.00 for a 2 gallon kit. I felt a little vindicated on my choice after finding a couple hot water tank manufacturers online that offered epoxy coated liners.


http://www.hotwater.com/lit/spec/storage/AOSTT35200.pdf

 

[Der Fuirmeister]

this is the reason I decided to launch into a one-off 409 stainless tank;

the delta -T between the max temp of your tank and the minimum effective output temp of your heating system defines the useful capacity of your storage

the closer to boil you can push your storage (which you cannot do with EPDM), the greater net effective heat storage you can acheive

pybyr, you used 409 SS. How is it working for you? Did you price other SS sheet such as 304 or 316?

After a year of researching, looking for the perfect answer to the tank liner question, I've decided to use SS. I'm gettin' too old to fool around with replacing EPDM in 5-10 years. Long story - short, I'm using SS because a 1100 gal. SS tank will only run $900 more than EPDM. And when it's done I will leak before it will. I also plan to run at 190-200* on a regular basis. This translates into getting ~30% more usable btu storage for the same size tank using SS vs. EPDM.

Your input or others would be appreciated.

 

[pybyr]

this is the reason I decided to launch into a one-off 409 stainless tank;

the delta -T between the max temp of your tank and the minimum effective output temp of your heating system defines the useful capacity of your storage

the closer to boil you can push your storage (which you cannot do with EPDM), the greater net effective heat storage you can acheive

pybyr, you used 409 SS. How is it working for you? Did you price other SS sheet such as 304 or 316?

After a year of researching, looking for the perfect answer to the tank liner question, I've decided to use SS. I'm gettin' too old to fool around with replacing EPDM in 5-10 years. Long story - short, I'm using SS because a 1100 gal. SS tank will only run $900 more than EPDM. And when it's done I will leak before it will. I also plan to run at 190-200* on a regular basis. This translates into getting ~30% more usable btu storage for the same size tank using SS vs. EPDM.

Your input or others would be appreciated.

When I went to have the tank fabricated, 409 was substantially less costly than 304 or 316, and it apparently discolors but does not corrode, which is OK for this application. My tank has water in it but has not really been put into use yet by actually being fully heated- need to finish some of the controls, and keep getting sidetracked with other projects. Truth be told, if I were starting afresh and couldn't use a propane tank (which'd be my first choice) I would probably go with an American Solartechnics tank.

 

[Der Fuirmeister]

Thanks for your input. I can't use a propane tank in the area I have. I've also looked at the American Solartechnics tank, but would like a larger tank. 900-1100 gal. would be the size. Since I'm off work I can fabricate a tank for roughly $1200-$1400. I'm looking at a grade 201 SS which is 15-20% cheaper than 304 (201 is $1.70 / lb in 12 ga. sheet), but have read some things about stress corrosion cracking above 60*C (140*F). I've also just found a geomembrane product designed for high temps. If that doesn't pan out I'll end up with SS.