what is sequestrant?

[unsrek1]

Our 25K in-ground pool was replastered with Pebble Fina on 7/9, but I just now read the Pool School article about new plaster. What is the 'sequestrant' that is mentioned? My pool contractor didn't mention anything about adding sequestrant. Their only instructions were to brush and backwash a lot during the first week. I had trouble getting the ph down, but after a week of adding muriatic acid it dropped to 7.3 and has stayed there pretty much since. I did start using my Polaris pool sweep about 6 days after the plastering, but I haven't noticed any resulting damage. And we had a pool party a week after plastering, so we may have started swimming too soon. The contractor said it would be okay.
Right now my chemicals all look pretty good:
Chlorine - 3
ph - 7.4
TA - 85
CH - 195
CYA - 20 (a little low, but pool is covered when not in use)

Should I still consider adding sequestrant?

 

[JasonLion]

During a new plaster startup metal stains can become incorporated into the plaster and become impossible to remove. Sequestrant binds to any metals in the water and prevents them from causing stains. You are already past the point where you would have had problems had there been any metals in the water, so there isn't much point adding sequestrant at this point.

 

[unsrek1]

Thanks. Any metals in the water would have had to come from our city water supply because I removed the rusty old heater from the circuit before firing up the pump.