We don't worry about phosphates. Pool stores will tell you phosphates matter but they don't. For properly sanitized pools maintaining TFP recommendations phosphates are irrelevant. Even if you have algae SLAM is effective regardless of phosphates. I think the main difference from TFP and the pool store is that we don't sell anything. Pool stores will sell you expensive algaecides that add metals and phosphates to your water. Then they'll sell you additional products to remove the metals and the phosphates. If they're lucky you'll plug your filters with these products and sell you filters also. Usually somewhere in that process pool owners get frustrated and end up here. Congrats! You may have saved yourself a lot of trouble and $!!
Your FC is too low for your CYA level. I'd take care of that first. Before you begin you may want to review thisABCs of Pool Water Chemistry. Ask any questions you may have. Please also fill in the rest of your information about your pool so we can get you better advice sooner. Here's how to add a signature.
This post will walk you through the anatomy of a sand filter, and then provide a video at the end for how to deep clean your sand filter. The filter used in the photos and videos is a Hayward S180T top mount sand filter. The images are of a similar filter. Obviously not all filters are...
I think you can see we truly do things differently from your local pool store. There are over 200,000 of us and many have been using this for over 10 years. TFP methods just work. It seems you're getting the hang of this from your questions and the responses you are getting. If you have any questions please do ask. There's no dumb questions here. In just a few days you'll realize there's nothing hard here. TFP is designed so that the average pool owner can do everything needed with simple science-based systems. Test results drive everything and you may be new to the testing procedures but your results are probably already better than the pool stores. While most pool owners use the simplistic TFP techniques we also have people that are true experts in water chemistry, fluid flow, electronics, automation, and almost ever aspect of pool construction. They are all available to you as a member.
An FC below 5 is an invitation for an algae bloom. Never let FC get below 5, 5 is the go/no go for algae! Your target for a CYA of 60 is 7-9 ppm.
I would worry more about that than PH. Your heater should be fine at 7.2. Folks do it all the time when slamming or during normal TA lowering.