@andrewiles - You are from Redmond WA, west of the Cascades. Your water quality should be excellent, absolutely no reason to need to mess around with your pH. West of the Cascades, your water is quite soft, low in dissolved solids, which means pH is a trivial problem.
Municipalities are required by law to buffer the pH of municipal water to a pH above 7.6 most aim for 8.0 When your total alkalinity is relatively low, less than 600 mg/liter as calcium carbonate, majority of plants have no trouble dealing with the pH.
I don't have a lot of time to re-type everything I have written on pH versus total alkalinity. Do look up some of my earlier essays. But to sum it up, except in a very few areas, pH is not the issue that needs correcting. It's a red herring. Total alkalinity is the horticultural significant water parameter. Total alkalinity is a measure of the BUFFER CAPACITY of the water. It is a measure of the amount of acid or base required to change the pH.
Water with a low total alkalinity, would require very little acid to lower the pH and very little base to raise the pH. Water with a high total alkalinity would require large amounts of acid to lower the pH, and large amounts of base to raise pH.
Plants can buffer the pH of the water film around the root tips and surrounding soil particles to their preferred pH by actively secreting buffers. This is the reason to not "over pot", in the right size pot, say half inch larger than the root ball, the roots can buffer the entire soil mass to the ideal pH. In an oversized pot, the roots can be overwhelmed if the pH of the soil is far from perfect. An example, measured in Sumatra, an orchid seedling growing on bare limestone rock, the water running down the rock cliff face, pH was 8.3 give or take. The pH of the water film surrounding the root tip of the orchid in contact with this rock and water was 5.4 measured by micro pH probe by James Asher of Unv Michigan.
Point is, plants, within reason, buffer their own root environment into their own preferred pH range, and do so quite efficiently.
IF the total alkalinity of your irrigation water is less than 600 mg/liter as Calcium Carbonate, for almost all the species of trees used for bonsai you will have zero problems. Carnivorous plants want water less than 100 mg/liter, Rhododendrons and azalea want less than 250 mg/lit. West of the the Cascades, in places like Redmond, I believe you have water that ranges from 60 mg/liter to 180 mg/liter. Check with your local municipal water supplier, their annual water report should include the average measured total alkalinity. If the report only includes total dissolved solids, total alkalinity can never exceed total dissolved solids. Alkalinity will always be less than dissolved solids.
So what I am saying, your concerns about pH are misguided. pH is not the problem. You are adjusting something that does not need to be adjusted.
