pHin will ask you questions during the setup process regarding the size of your pool and ship you the chemicals you need. Our subscription is based on a conservative estimate of average residential pools.
There are a number of factors that contribute to the amount of chemicals needed to maintain your pool. Size is obviously one of them but if you use a pool cover, that can help tremendously. Weather and the number of swimmers each week also play a role (among other things).
We expect that the vast majority (90% or so) of our customers will not need to be charged extra for additional chemicals. If we detect much higher than normal chemical usage, we'll reach out to you to discuss options and potentially identify ways to reduce your chemical consumption.