Indirect Tank - Plastic vs Stainless

jad3675

I'm in the middle of researching IDW tanks and all things being equal, is there a reason I should choose a stainless tank vs a thermoplastic tank? Burnham LT tanks are slightly cheaper size for size vs a comparable stainless. I'm on city water (Cincinnati, Ohio) and per the published water quality reports I'm well within the chloride limits for 316L stainless, so the tank getting chewed away on the inside isn't a big concern.

Thanks,
John

Larry Weingarten

Hi, I'd compare warranties, insulation levels and support available for the different tanks in your area and let that help you make a decision.

Yours, Larry

jad3675

Fair points, Larry - local supply house sells Weil-McLain and Burhman. WM makes a SS and Plastic tank, which have comparable specs to the Burnham plastic tanks, though the WM plastic tanks are far more expensive than the SS and the Burnham plastic is the cheapest of all. Burnham can be had with a lifetime warranty if you send a check in. Otherwise the warranties are roughly the same (12 on WM, 10 on Burnham). First hour numbers are about the same for comparable sized tanks.
I'd be able to go bigger with the cheaper plastic, though.

mattmia2

Look at your water chemistry and the specs for the tanks too. Neither likes water with a lot of chloride.

JohnNY

I love the idea of stainless steel tanks and a better warranty is my go-to option for proposals to clients for their perceived value. As far as first-hour recovery, those numbers are highly manipulated. I compare surface area of the heat exchanger instead.

jad3675

John -
Thanks - that makes sense, and yes I had read how they game those FH ratings. So, as far as SS tanks go, Heat-Flo seems pretty highly regarded. My local supply houses list them and can get them as a special order, but they do not stock the or sell them. Is that a big issue? I mean, it's a metal tank that holds water - not a lot of moving parts to go bad. Either it is holding water or it isn't, right?

John

STEVEusaPA

I personally am a little concerned about plastic tanks, especially if they claim maximum temp of 180°. Not hard to run up and over that temperature for a number of reasons. Hate to see that void a warranty.

mattmia2

I dug in to this a little more and am curious about why I can't find water chemistry requirements for plastic tanks, or at least the weil mcclain.

If it is going to a modcon you might think about versions with 2 heat exchangers to get lower rwt under light to moderate draw.

hot_rod

composite indirects are fairly new to the market. The temperature limitations, are they for the tank operating temperature and the SWT to the coils? Many boilers run up to and above 180F on a DHW demand.

jad3675

Yeah, one of my concerns was the water having a bit of plasticky taste/smell at the tap if the temp was too high. It's not like these are some fly-by-night operations making them, though so you'd think they'd be pretty safe in that regard....