If muriatic acid is safe to pH the water in swimming pools can water that is just pH'ed with the acid be used on house plants?
If the water you are intending to use has been brought to Ph of 7.2 as is normally done in swimming pools then there is no problem at all using it to water plants.
No. Do not use this acid mixed with anything to water your houseplants. Muriatic acid is extremely dangerous and is a matter between life or death
Please check out the weblink at the lower left and you will see why. You can also ask an employee of a pool supply company if this is a dangerous practice or not.