I'm going to take this opportunity to rant a little. The entire manufacturer/wholesaler/dealer system sucks. I took the hours on google to figure out what I needed, then I went to the manufacturers website and used their calculators to work out exactly what model would do it. Then when I couldn't find pricing I sent them a message asking how much? They forwarded that on to a distributor who got back to me anywhere from over night to never with most being about a week. They said go to these local businesses as we supply them. So I drove down and spoke with multiple local businesses which all said hmm yeah they're a supplier lets check the computer. Nope not in the computer ok we'll call them. So they called the distributors while I waited and the distributors turned around said they'll need to call the manufacturers and will get back to me with the price.
This happened on the GEA heat exchangers. Each person down the line was adding a nice little chunk to the price and in the end the best I got was we have a dw4-8 listed and it would be almost $500 so I said $500? the guy quickly did some math and bam $600+tax which in my mind means he just added $100 to his cost. The other guys I spoke to are still waiting to hear back from someone.
I was wanting to go with a Rheem Marathon MTS85345 or a CMTS85345 (apparently the canadian version is a bit different numbers wise). It's a 85 gallon tank with one backup heating element up high and two lower ports to circulate through the heat exchanger. They have lifetime warranties so long as I keep temps below 180F or so which is fine.
How often as a retailer do you get someone coming in saying give me X how much? Well they can't find it in the system. I instead got pricing on a MR75238 which is a 75 gallon regular dual element heater tank by the sounds of it. Looking online I can find specs but not a drawing so far... So this means drawing #6 for the inspector....
Anyways that's a horrible way to do business. Customers that know exactly what they want and have cash in pocket shouldn't have to be told we'll see if we can find one of those and figure it out. I also shouldn't have to be gouged by every person between me and the manufacturer. I spoke directly to 3 different heat exchanger manufacturers and all 3 passed me on to other people who couldn't give me a price without going back to the manufacturer. All 3 have now lost my business.
My current plan is to go with the 75 gallon marathon tank. Cost wise it's looking like my best choice out there for being the last hot water tank I'll ever have to buy. I'll have to figure out the plumbing to circulate out of the drain and back into the cold input or a port if it's available. For the heat exchangers Ebay and google both gave me dudadiesel this model in particular
DudaDiesel.com Biodiesel Supplies
It's bigger then the dw4-6 in surface area so I'll need to redo the math. It's also 304 stainless not the 316 stainless I was hoping for. How much difference it will really make in the long run I don't know. looking around 304 is pretty damn common for lots of things and they just don't recommend using it with salt water. Anyways realistically the heat exchanger is more likely to fail due to clogging then rusting out.