First things first install a laing autocirc recirculating pump in the up stairs bathroom under the lav sink in the cabnite. If you dont have a plugin under the cabnite you will need a sparky. The pump will maintaine a 98deg temp. second if local code permits i would install a small expansion tank along booster pump fed through a check valve and if not equiped with internal pressure switch than install a seperate one Don’t forget a safty pressure relief valve vented to your drain system. Strongly recommend this all be professonially installed.