Im not sure if you know but most tankless hot water heaters adjust temperature accordingly to intake water temperature. It self regulates flow output from the inlet water temperature. Meaining the hotter the intake the less flow on output. Now the issuse is most tankless can only intake a certain temp. Mine was 92f. So to fix this I had a 55 gallon drum reservoir. I sticked a slump pump for flow towards the tankless. My output from the CLS was a hose positioned 6 inches away from the pump in width and the tip of the hose was a few inches to flush with the the the top of the slump pump. This position made my water have a steady hot/cold ratio that kept temperatures below the threshold of 92 throughout the recovery. If you deciderd to this make sure you use DI water or RO.