My water tested low for PH at the pool store, the guy told me to add Metal Free before adding the soda ash because I have a heater and there will be copper in the water even though I told him I have a heat pump with a titanium heat exchanger(Aquacal H120). He then tested for copper and the dip strip showed fine, he was still convinced there would be copper in the water and the soda ash would not be able to work with it in there.

I am not sure if there is any copper in the heat pump that comes into contact with the water, only thing that might have copper is a spigot on my homemade solar heater to drain it for winter but that is probably brass.

Should I add the Metal Free before I start to add the soda ash to raise the PH?

-Thanks.