Pool Era field notes · Missouri pools
Closing a Pool for a Missouri Winter
First freeze on the way and not sure when to close the pool? In Missouri, the timing and the plumbing matter most.
Water left in the lines can freeze, expand and crack pipes and equipment. Here is how a closing usually goes.
Timing
Close before the first hard freeze.
University of Missouri Extension says central Missouri usually sees its first freeze around October 20, and southern Missouri around November 1. The Ozarks tend to freeze earlier because of their higher elevation.[1]
MU Extension's Missouri Frost/Freeze Probabilities Guide shows likely dates by county.[1] Use it to pick a closing date with some cushion.
Why
Why freezing water does damage.
A National Institutes of Health technical bulletin says frozen water takes up 9% more space than liquid water. When water in a crack or pore freezes, it pushes outward, and repeated freezing and thawing can widen cracks over time.[2]
That is why the lines, the equipment and the deck get the most attention in a Missouri closing.
Steps
What a closing usually includes.
- Clean and brush. Pentair, a pool equipment maker, suggests a deep clean and a good scrub of the walls first.
- Balance and shock. Pentair says to balance the water and shock it before adding winter chemicals.
- Lower the water and drain the equipment. Pentair lists lowering the water level, draining equipment and removing the drain plugs.
- Blow out the lines. A pro blows the water out of the equipment lines and often plugs the skimmer, to lower the chance of frozen pipes.
- Store equipment. Pentair suggests a dry spot that stays above 40°F for equipment you remove.
- Cover it. Check the winter cover for holes. Water bags can help hold it down on an in-ground pool.[3]
Over winter
Check on it a few times.
If you can reach the water by releasing a corner of the cover, Pentair suggests checking the chemical levels and adding chlorine about once a month if needed.[3] Keep heavy snow and standing water off the cover.
Every pool is set up differently, and your equipment maker's manual has the steps for your heater, pump and filter. See Pool Era in Missouri for what we do there.
Related
More field notes
Missouri poolsOpening a Pool in a Missouri SpringCover off, water back up, chemistry checked before anyone swims.Read 
Finishes and renovationSigns It's Time to Replaster Your Pool (and When It Isn't)Rough spots, stains and worn patches: when to replaster and when it is just the water.Read 
Care and ownershipIs My Pool Leaking or Just Evaporating?How to run a bucket test, and the signs that point to a real leak.Read
Sources
Where these facts come from
- University of Missouri Extension: Average first frost (Missouri Frost/Freeze Probabilities Guide)
- National Institutes of Health, Office of Research Facilities: The Freeze-Thaw Cycle in Concrete and Brick Assemblies (2019)
- Pentair: How To Winterize a Pool
Sources checked October 25, 2026. Frost dates are long-run averages; check the MU Extension guide for your county.
Before you rely on this. This field note is general information, not professional, engineering or legal advice. Every pool and every site is different. What Pool Era does on your project, how and with what warranty, is only what your written agreement says. Local codes and HOA rules change, so check with your city, county or HOA before you rely on anything here. Website terms
