When you have a successfully operating service business, I completely agree that you should cautiously *TRY* a new method, before rolling it out for all your customers. There are going to be local variations in what's needed, to make it work in your area.

Beyond that, it's up to you. I don't know what pool chemicals are sold in your area, what typical pool and filtration systems are like, what the code requirements are, and more.

But, what I can tell you is that, if you are in pool chemical sales in the USA, there are 3 possible attributes you can have:
1. you can be knowledgeable
2. you can be honest
3. you can be an aggressive salesman of profitable chemicals

But, you can only have 2 of those 3 attributes at any one time: you can't be knowledgeable AND honest AND sell the profitable chemicals.

When I first started PoolSolutions, I fairly regularly got what I called 'nasty-grams' -- emails or phone calls of the "you traitor to your trade" variety. I found those amusing, and used to have a page publishing them. But, I remember one call from a lady who very much wanted to be honest, but who had a profitable pool chemical store selling chemicals that her customers didn't need. She was almost in tears, because she was afraid that I was right, but couldn't figure out how to keep her business AND be honest, now that she was more knowledgeable. She didn't do pool service, so I couldn't help her, which I greatly regretted.

But, since you do service, there may be another option.

Pool owners don't "want" chemicals; they "want" their pool to be right. When I started doing commercial pool service, I rapidly discovered that, the better the job I did on the pool, the less I made selling chemicals. I switched to flat fee service, typically charging $2500 - $4500 per season for all chemicals and service it took to make the water right. The customer had to agree to let me train their staff, and enforce water checks every 3 - 4 hours, and I agreed to come as often as needed, and with as much chlorine as needed. They were happy, because they'd often been spending more than that on chemicals alone. I was happy, because labor and chemicals were costing me about 1/2 of that. Later, I got smarter, and tried to set my prices at 10% OVER what they'd paid for chemicals alone . . . and they were still happy.

But, I made a serious mistake that ended up costing me most of my business. I'll warn you, so you don't do the same.

With commercial pools, staff tends to change from year to year, and after three years, typically none of the people who hired me -- and who remembered how badly the pool had run before -- were still at the pool. They'd heard about it, though. But, after six years, the staff simply assumed that the way their pool ran was the way pools mostly ran, and thus, that I was doing nothing special.

So, when someone came along promising them the moon, they got suckered; I lost my contract; and afterward they were too embarrassed to admit the mistake and hire me back.

What I SHOULD have done is collected info (photos, if possible) of how the pool had run BEFORE, and then continued to market my services to my NEW customers (old pool; new staff!) with annual newsletters and such that documented what their pool had been like before. Doing so would have allowed me to keep many of those customers much longer.

So, if you choose to go to flat fee service with your customers . . . then the money you save on chemicals will be yours. But, you need to make sure to continue "selling" the very real benefits of your service to your customers, so they don't get suckered by the flashy promises of your competitors.