So I bought a farm, with a 200+ year old updated farmhouse. Water supply is 1in from a PSD and varies between 50 and 70 psi. I've owned the house a month and a selling point was the 9 year old carrier geothermal hp with desuperheater. 2 weeks into owning it the 26yr old 50gal electric WH blew up out the hot out top nipple.

I've replaced water lines and WH before. I'm not familiar with desuperheater configurations and this single WH setup doesn't fit any diagram on-line. I'm also aware that without a buffer tank I'm not getting the benefits I should. I need help.

1. Originally it was drawing to the DHW in from the drain T. Drawn up to a T with the main IN. The main IN went to other fixtures cold and T's to the drain and DHW in. I've read this isn't recommended due to the sediment draw into the desuperheater. The DSH out went into a T with an expansion tank and into the DHW cold inlet. Almost all lines were dropped to 1/2 even though the main coming out of the softener is 3/4 but they necked it down immediately.

2. I want to stick with 3/4 pex to a few feet from each branch and then drop to 1/2 for fixtures. The water heater and DSH are approx 25 ft apart so I plan to T off 3/4 cold pex to 1/2 copper for the DSH in and out legs and then pipe DSH into WH drain.

3. I'm planning my T to the DSH to have a stop and waste valve and a 1/2" swing valve but I'm not sure if the stop and waste valve covers the "venting waste valve" recommendations I've seen in the Bergy diagram but I can only see the 2 tank setup.

I replaced the expansion tank with a Thermal Expansion Valve and Vacuum Relief Valve but the DSH is still coming in that location. I need to reroute it to the bottom and make sure the WH inlet doesn't have a check valve. Are there any parts I'm missing other than meeting the requirement of the venting waste valve requirement. Because the DSH will be separated from the Thermal Expansion Valve should I cut in the cold-in pipe an expansion valve or any additional vacuum relief or backflow values.

Thanks for any help you can provide. I'll try to attach two images. Simplest is the basic original layout which looks off to me but similar to how some people described installs from one model but not Carrier. The second image is more of a rough sketch of the full WH in and out plumbing diagram. The second image appears to be too large but if my description isn't enough I'll try to capture it in a different image format and upload.

Got that second diagram with the planned layout resized below