Is it worth it to spend the money on a stainless IDHW or save a lot of money on HDPE?

What are the benefits? Downsides?  Is there BPA in the HDPE?  Any other possible health affects?

What is a IDHW?

Indirect hot water... almost always ran of boiler supplying radiant heat. Every modulating condensing boiler that I have read about is set up to support it..


HDPE = lined with high density poly ethylene
Stainless = the obvious

Two ways of dealing with water in contact with metal

there is always a glass lined unit as well. that's pretty inert.

IWH,

I have installed nearly all available (next week the new economy priced, plastic-lined "Champion" by Amtrol. Rheem has made the electric super-insulated "Marathon" for years and they seem to hold up very well. The cheapest IWH outlast the best conventional glass-lined water heater. Glass, plastic, stainless, all NSF, which is all I need. Price and quality do not always line up. "Stainless" is a near meaningless term, but all of the SS models seem to hold up.

The heat exchanger or coil employed is of more interest to me. The Buderus glass lined tank and coil can be shocked to dislodge lime buildup (does not work on "finned" heat exchangers). Naturally if you can afford an IWH, you should have soft water.

Avoid the useless "double-wall" unless you are bent on introducing toxic chemicals to the heating system. I understand that Buderus and Triangle Tube sell single wall indirect or "companion" water heaters all over the world, but do not make a double-wall indirect.

There is no better high efficiency domestic hot water heater made than the combination of ModCon and Indirect-fired water heater (IWH).