All of the alk supplements, including sodium carbonate/washing soda/soda ash should only be added when you are below your alk target and want to raise alkalinity.
Any pH effect they give (up or down) is a "bonus" and should never be the driving force behind dosing amounts because it can lead to excessive alkalinity.
War flow in the tank may actually lower pH, not raise it. Forget internet searching for topics like that which has far too much misinformation and stick to Reef2Reef for answers to questions related to aquarium chemistry.
There are lots of good ways to deal with pH issues, but the first step would be to measure alkalinity.
Second comment is that pH kits are not the best way to measure pH, and pH is not a priority measurement in most tanks.
This has more:
by Randy Holmes-Farley For many aquarists, pH is not something that they have much experience with aside from their aquarium. For many, pH is almost a black box measurement: something to be considered, but whose physical meaning makes little sense to them. This article will Read more here...
www.reefedition.com
