Water Temp On closing and Algae

JoeRJGR

Well-known member
Jun 19, 2013
138
Freehold NJ
#1
Not sure I understand the common logic of waiting for the pool water to drop below 65 or 60 degrees before closing. My water is at 72 right now, next week outside temps are suppose to go into the 80's.. Assuming I close with my solid cover today and the temps rise and my chlorine levels don't hold...I suppose the logic is I'll get an algae bloom. OK, but that algae will continue to survive in 30 degree water temperatures all winter long till I open in the spring?

Opinions please...
 

pabeader

LifeTime Supporter
TFP Guide
May 14, 2015
4,349
Cartersville Ga
#2
The algae might not survive, but their effect will. If the water is clear when you close and you close when it's too cold for algae to grow; then when you open in late winter early spring, the chances are much greater that you will still be clear.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
#3
We recommend colder water at closing simply because organic matter activity slows down dramatically. This reduces the likely hood of a major algae outbreak. In addition, the colder water couple with less sunlight, uses far less chlorine. Closing/covering your pool at warmer temps only locks-in active organic material increasing the potential for an outbreak.
Pool School - Closing an In Ground Pool
 

Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,289
NW Ohio
#4
A frozen block of green ice in winter is green water in the spring.

I'm one here who is not hard-lined on closing late or opening early, but as with all TFP recommendations you should be prepared to deal with the aftermath of not following them. I help close pools with warm water and they almost universally need cleared in the spring, but that is the owner's decision and their money to spend clearing it up. I follow the 60 degree rule with my own pool and not only do I open to clear water but I also still have measurable chlorine in my pool when I open nearly 6 months later. Last year I actually didn't have to do a thing to the water upon opening, the levels were perfect. For me it's worth waiting, especially since the lower sun angle and cooler water significantly decreases chlorine usage during those fringe months.
 

JoeRJGR

Well-known member
Jun 19, 2013
138
Freehold NJ
#5
Thanks for the replies....couple things to note:

1. I use a hard cover so there will be no sunlight.
2. My question really revolves around the fact that in a worse case scenario getting an Algae bloom in the fall will have what effect in the spring? Water temperatures will be at least in the 30's.....the algae will be dead...no? Donldson mentions cleaning that up in spring...I get that...but it wont survive correct?

- - - Updated - - -

I will say I have never had measurable chlorine upon opening....never been green, but never had chlorine.....I would think opening early is more important closing late.
 

Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,289
NW Ohio
#6
Algae doesn't grow in cold water, but that doesn't mean it dies. Even if the algae that was frozen solid were to die (which I don't believe it does) an IG pool never freezes through. There will be plenty of live algae in the pool, just waiting for its chance.
 

Pool_Medic

Well-known member
Apr 1, 2018
436
Bangor Maine
#7
I close my pool every year mid September, water temps between 68-72. Raise chlorine 2-3 days before closing, insure the pools sparkling clean, close n add poly quat 60

22 years and it’s crystal clear come spring. But we get cold temps faster than most. Our nighttime temps now hover around 40-60
 

Marty D

Well-known member
Jun 16, 2016
357
Quogue new york
#9
I close my pool every year mid September, water temps between 68-72. Raise chlorine 2-3 days before closing, insure the pools sparkling clean, close n add poly quat 60

22 years and it’s crystal clear come spring. But we get cold temps faster than most. Our nighttime temps now hover around 40-60
Same here. I will be closing Monday and this weekend my pool water is 89 -heater is on. Monday I will put in poly -60. That’s the key.
 

Catanzaro

Platinum Supporter
TFP Guide
Jul 30, 2014
3,207
Monmouth County, New Jersey
#10
I close my pool every year mid September, water temps between 68-72. Raise chlorine 2-3 days before closing, insure the pools sparkling clean, close n add poly quat 6022 years and it’s crystal clear come spring. But we get cold temps faster than most. Our nighttime temps now hover around 40-60
Pool Medic:

One thing missing is the cover. What type of cover do you have? A less expensive mesh cover in Mid September can almost guarantee a problem if the pool is opened late in the spring near the holiday. A solid cover will probably work. My pool was closed Mid September one year by PB (first year only before started doing myself), but he pool was opened super early without a problem. One of the key components is the solid cover.

You never added your signature? Thanks!