I'm looking into buying a Marathon thermal storage tank for a desuperheater of a waterfurnace geothermal system.

I have a few questions. (I've seen similar questions online but haven't found satisfactory answers.) Please let me know if you know anything about any of these.

1. Is the interior lining of the Marathon polybutene-1, i.e., polybutylene, or is it the oligimer polybutene? If it's polybutylene, why is it expected to be any more durable/better than the pipes and pipe fittings that are now considered a horrible thing to have in your home? (Even if it has a lifetime warranty, I'm not going to be happy if I have to replace it and/or it floods my basement.)

2. Anyone know why the storage tank without a heating element costs significantly more than the one with a heating element? I don't need or want the heating element, but should I buy a tank with a heating element anyway? Pros/cons?

3. Where do you find official numbers on the standby energy loss of the tanks?

4. Is the polybutene safe? Will it leech chemicals into the water?

Thanks.