What does the pool look like? Are they separate? How about some more pictures. Overall pool setup, closeups of more of these dings and those spots on the floor. A picture of the equipment pad. Also some water test results.
Pool School - ABCs of Pool Water Chemistry Cl cc calcum hardness ph. Use a drop based test -- no strips. Historically do you know what those numbers have been.
The pool is a rectangle with the spa centered on one long side of the rectangle. They are joined together and the spa circulates into the pool while the main pump is running (and valves are pointed toward the pool side). I can take pictures tomorrow morning as I'm at work now and it will be dark when I get home. Equipment that I can recall off the top of my head: Inteliflow VS-3050 pump, 58 sq/ft DE filter, single speed spa jet pump, old looking cast bronze heater.
Historically I do not know the numbers. I have ordered the TF-100 test kit and will be using that as soon as it shows up. The current kit I have may be fine, but since it was left by the previous homeowner I have know idea on the age of the reagents. I have taken water samples to a Leslie's two times in the last two weeks. The CYA levels were different each time which made me think the test was, perhaps, subjective in some way. First time was 120 and then two days ago (after which I ordered the TF-100) it was 80. No draining or reverse osmosis on my end. PH was 7.6 which matches my at home test.
According to the employee during my last test at Leslie's my water is perfect and I should put the test results on my refrigerator. However FC was 3ppm which at 80 CYA seems low to me. In any event I can get you more helpful info on good numbers when the TF-100 shows up. As far as I am aware CH was not tested unless that is what they are calling total dissolved solids.
Here are the Leslie's numbers: FC: 3.0ppm, TAC 3.0ppm, CYA 80ppm, TA 100ppm, pH 7.6, Copper 0ppm, Iron 0ppm, Total Dissolved Solids 950, Pho 50ppb
When you tap the plaster does it sound hollow anywhere?
When we get all that we can give you a better idea.
That is a good question and although I'm not really sure exactly what to listen for I can give it a shot.
But a few quick thoughts. How old is the pool? Because I think your plaster is old and is beyond its useful life. Depending on how the pool looks you may want to have it all replastered. What are those spots on the floor?
Anyway try and respond to the questions above -- the plaster experts may be along in a day or so and ask more questions and use what you provide to impart more wisdom than I have.
Pool age is unknown to me. The people I bought it from said it was already in when they bought the house 15 years ago. They said they had it re-plastered 7 years ago.
Spots on the floor are holes for a blower to make the spa crazy. It is kinda fun to watch.
Thank you for your time!
-Jeff