Green pool & sand filter - first step?

[AussieSwimmer]

Hello all,

I am new to sand filters. I am in charge of an apx 15,000 gal outdoor pool that is densely green (Atlantic region of the US, so we're slowly starting to exit a harsh winter here). The pool is coupled to a Hayward S220T sand filter, and Hayward Aquarite AQR3 chlorinator. The pool was winterized by a company, and I have found the fittings bagged and left in the pump strainer basket.

Once fittings are returned to operating locations, would the first step be to circulate water thru sand filter, and leave the chlorinator offline? Or should I attack the water with chemicals first, and focus on vacuuming out what I can? I can visualize that pumping the water thru the filter in it's current state is going to quickly clog the filter, and that frequent cleanings will be required. On the other hand, material removed from the circulating water is that which doesn't need to be consuming chemicals.

Thanks in advance! - G.

[Teapot1]

Add liquid chlorine first but test the pH of the water and the cyanuric acid (CYA) but not with dip strips and see where those are. You want to see the green turn to blue/grey (a sign of dead algae) the chlorine will get used up pretty quickly killing the algae so you'll have to add more after a few hours. I would start with 5 gallons.
Yes the filter will get a bit clogged so just backwash when the pressure rises by 6 psi or so. Remember to use the rinse after backwashing before going back into filtration.

[AussieSwimmer]

Good morning Teapot1, and thanks much - this is great.

I have 2 additional things to mention....

1. The pool care team hired last summer overdosed the pool with salt. Is a salt pen the right independent tool for checking for current levels? (I think they got an erroneous reading from the Hayward chlorinator while replacing the salt cell - seems like a bit of a rookie mistake for a pro to make??). Is it important to establish correct salt ppm prior to getting treatment underway? Or can that parameter be handled once the killing-and-filtering is largely done?

2. With the initial shocking, I would of course want to keep the chlorinator inactive. Is it as simple as keeping the controller setting on zero? I don't see anything specific to this scenario in the Hayward manual.

In appreciation - Grant.