are there any reasons why i cannot use my indirect WH as a buffer tank for my in floor load?  any tips on proper piping?
btw, this is on a TTsolo110 and smart 40   THX

yes. if you do that, you turn every heat demand into a domestic demand. Which means not much condensing and no modulation.

much more efficient to use another tank that runs at heating temps and doesn't cause the solo to go to max fire.

thanks rob. the way the tt solo is set up with dhw in priority, so the controller tells the boiler to fire at max when there is dhw call. but if the tstat calls for heat the boiler can do what its designed to do (modulate, and run at 134 target temp). what i'm trying to achieve is to run the water thru the indirect on its way to my load. therefore the boiler would operate the same way its just that the piping would route thru the indirect (i could put in a t after the dhw circulator and connect the return to my primary loop for instance) does this make sense?

the only way that would make sense is if you were not using outdoor reset on the heating, which you should absolutely be doing. with reset, you will run below domestic storage temp much of the time.