What did I fail to do?

[St8kout]

It took almost 3 weeks to clear out the green soup in my pool after being covered all winter long. After I got the ph level down to around 7.4 and kept the chlorine levels in the 20s the water finally cleared up. Once the chlorine level dropped to around 4 ppm I put my solar cover back on. Now, after only 2 days the water is green again with algae growing on the pool walls. What's going on? Does the blue solar cover encourage algae growth or something?

Ph=7.5
Cya=48
FC=4.5

[Watermom]

Did you continue to test and maintain the chlorine level while the cover was on?

[sunlove]

How much ppm are you losing overnight? It sounds like the chlorine level got too low and it was still fighting an algae bloom...

[St8kout]

I was out of chlorine reagent for four days so I was going by how red the water turned after adding DPD, as I had been testing it everyday and thought I had a handle on reading it. From the "Best Guess Chart" I need a minimum of 3ppm and it looked like I was within range. Obviously, I need a higher minimum since my zombie algae found a way to come back from the dead. Sigh.

It's more tricky than I thought trying to keep the chlorine level safe enough to use the solar cover yet high enough to prevent algae growth. Of course, I'm using the solar cover more for preventing evaporation than for heating the pool. I was surprised by how fast the water level can drop during the summers here, and the cover makes a big difference. It more than paid for itself as reflected in my water bill.

[Watermom]

Have you been running the pump while your solar cover has been on the pool? If not, do so. Aim the eyeball down away from the surface so it won't push your cover out of place but do run the pump.

[St8kout]

Have you been running the pump while your solar cover has been on the pool? If not, do so. Aim the eyeball down away from the surface so it won't push your cover out of place but do run the pump.

I did but obviously not long enough. I had been running it all day everyday for 3 weeks to clear up the original green soup mess and after it was clear I thought I could get away with a just a few hours a day.

On a side note, I'm starting to realize that it would have been much easier and cheaper to just drain the pool and refill when I first pulled the cover off. I spent more on chemicals than what the water would have cost to refill, not to mention all the time spent having to clean the filters 2 or 3 times a day as they got clogged up pretty fast. The only downside is I would have to buy/rent a water pump as my system has no backwash or drain to outside of the system. The ground is really dry here in Nevada so there is not much risk having an empty pool for a short time. Live and learn.