In my State the code compliance, and inspection guys can be different. One has a check list of things to check, not a list of what equipment the properties have. I could move the entire pump room to the other side of a building and they wouldn't know the difference.
Many times they only check for the same list of about ten items, they pencil whip the drain covers, because they didn't bring their scuba gear. They look for signs, shepherd hooks, lift buoys, emergency phones, spa shut offs, flow meters, gauges, gates and gate locks, the pool light, and they may or may not check ALL the chems.
We have some in the same city that might check all of that, or some that hardly check for one third of above. Their thing seems to be they want to find something stupid for you to fix, many times it's not on their check list if they even have one. They pass over little things all the time and we darn sure don't point it out if we are missing it or if it's broke. We just go back later to rectify it on our own. This summer the same dude inspected 5 pools and didn't even have a test kit. And of course our person walking with him was out of R13 and R4. How convenient for us right? No cya or Ph test. lol
If we pull a permit, a different code compliance guy will come out after weeks of back and forth paper work and fees. Before during and after the job is complete. Now that dude knows much more about what he is doing. Our rule of thumb is if you are not building something, or tearing it down, you almost never need a permit. Replacing something, like a filter, or timer is just that. Forget about different models, nomenclatures, or minor size differences your replacing or adding, and just focus on what the States intent is. Does what your replacing change the danger to you or others. Are you building something new, or adding to in a meaningful way, or taking away from a small structure. Like filling in a spa. From what I have read, no you are not. But I know nothing about your State or City.
Don't take this wrong, you are probably the kind of guy that will talk yourself into needing a permit that you do not really need. You need to be able to speak, ask, and answer questions about the above in whatever language they speak in. Like having a lawyer in court with a judge.
Somewhere in your city, there is an office with a little window and some lady sitting behind it that knows absolutely nothing about whatever your asking about. Like when you go to the DMV. Get passed her, and her supervisor, to get the number of the "guy" that knows about what your asking. The one who would go out to inspect for permits. Those ladies are going to give you several packets with forms that have nothing to do with you. Sometimes we spend weeks trying to get a permit for stuff we don't need permits for but all that paper work they give us implied that we do need a permit. You'll only get one shot asking that "guy" your questions, and how you answer his. If you make a mistake that you never knew were mistakes and he says you need a permit, your stuck with that guy now, and your on his radar. Changing his mind will be harder than having the right answer the first time.
" The flow rate on this pool is to low for it's size. How many gallons is this pool are you sure it's 45,000 gal?
What! No! That's way high, this is only about 32,000 gal, take away the steps, benches, and sun bathers it's no where near 45K.
Well that makes much more since on the flow rates".
"Yeah we're good here. "
Can you imagine answering that one simple question wrong?
Get a contractor to ask those questions for you if you truly are in a grey area. Like James said they should know the answer already.
I will say this when putting a bid together to get a job the contractors are going to want you to pay less to the Govt if they can. You seem to be worried about getting good bids from contractors. Why? Do they charge for quotes up there? Down here they are free and none binding. I don't see a downside of having lots of bids. The only money you are going to shave off from advice here will be on the items price if you buy them yourself, not the labor. TX, FL, CA, or HI are never going to compare against your contractor bids, in what I must say is a messed up state from what in hearing.