How to Winterize Your Swimming Pool

by Pool Builders on 09-06-2010 in Articles

Pool closing or winterizing can be a little more time consuming than opening or regular maintenance, but doing it the right way protects your investment and provides a cleaner, simpler opening the following spring. The simplest way to provide you with the correct information is this format of a checklist.

Use this checklist to make sure that you've done what's needed to winterize your pool the correct way so you can open up to a clean pool next spring.

Something to keep in mind when winterizing: Your pool water WILL freeze! Depending on where in the country you live, there may be a thin sheet of ice or it may freeze almost solid.  The ONLY way to keep the pool from freezing is to turn it into a giant Martini. Be sure to check with your local builder if there are certain pool system items that require special attention.

First off, please consider doing TWO things about 2 weeks prior to closing your pool. Add a good Natural Enzyme product to "eat up" accumulations of greases, oils and other non-filtered organic waste in the pool. The second thing to consider treating is the bio-film growing on all of the pool surfaces - on the pool itself, in the filter system, in the plumbing lines, behind lights and ladders, etc. Bio-films directly contribute to the growth of white water mold, pink slime, scale and algae, not to mention significant problems such as Chlorine Demand and poor water balance. Please see my other articles dealing with these issues.

If you are or have been dealing any water quality issues such as algae or cloudy water or the pH being off, correct those problems BEFORE winterizing. Ignoring the problem now will only make it worse in the spring. Algae, white water mold and pink slime do not die over the winter, they only go dormant.

Adjust the water balance: pH 7.4 - 7.6, Total Alkalinity 90 - 130 ppm in vinyl or fiberglass pools, 80 - 120 ppm for gunite or plaster finish pools. Calcium hardness should be corrected to prevent long term pool surface degradation; a range of 175 - 250 ppm for all pools in acceptable. Water balance is especially crucial with freshly plastered gunite pools (done within 90 days of pool closing) to prevent staining and mottling of the new surface.

Let's go step by step and winterize the pool.

ALL POOLS (vinyl liner only):

[  ] Remove the ladders and any deck equipment

[  ] Vacuum the pool and remove all leaves and debris

[  ] Clean and protect the waterline with a good gel-type pool surface cleaner. Do not use household cleaners on vinyl liners. This type of cleaner will help prevent a dirty water line build up over the winter.

[  ] Drain the Filter tank of ALL WATER. Leave winter drain plug off!

[  ] Put all eyeballs, drain caps, gauges, etc. in the pump basket for safekeeping. That way you know where everything is next spring.

[  ] Clean DE filter grids or Cartridge with a good Pool Filter Cleaner. Do NOT use muriatic or sulfuric acid as these products will set the accumulated greases & oils into the fabric of the DE grids or Cartridge material. Consider using a quality enzyme based filter cleaner - tough on dirt, easy on the environment.

[  ] Bring the pump/motor indoors for winter and store it in a cool, dry place.

[  ] Winterize the heater (if equipped) according to the manufacturer's instructions. Failure to do so will cause winter damage and freezing. Be sure it is properly drained. As an extra measure, it is a very good idea to flush the heater with a good non-toxic pipeline Anti-freeze. If you have field mice in the area, add a mouse repellent to the heater area. Mice love to chew on wiring and build nests in the heater.

[  ] Remove the return eyeball(s) and install plug(s) or cap(s).

[  ] Winterize the skimmer(s). See below for pool type

[  ] Put on the Winter Cover. 

All Solid covers should FLOAT on the top of the water. Remember that mesh covers will immediately allow pool water to come UP from underneath the cover. Pools utilizing a mesh cover should consider DOUBLING the amount of winter shock and algicide to prevent algae growth. 

DO NOT drain pool lower than bottom of skimmer (mesh covered pools only)

If a pillow is used to hold up the cover, inflate it to only to about 2/3 full. Over inflation will cause air leakage and subsequent DE-flation of the air pillow.

[  ] Properly store the pool's maintenance equipment such as the vacuum, net, pole, etc. Automatic pool cleaners should be cleaned and rinsed of any dirt and silt. 

INGROUND POOLS (vinyl liner only):

[  ] Thoroughly blow out the underground lines

[  ]Install Gizzmo(s) in the skimmer(s) or use an Aquador(s)

[  ] Add a good non-toxic pipeline antifreeze at the rate of about 1 gal. per 20 foot of line pipe run

[  ] Store the diving board (if equipped) in a flat, horizontal position

[  ] Safety covers should be re-tightened at time of installation

[  ] Add an additional dosage of Back Up Algicide in the spring (before opening) if a safety cover is used


[  ] Winterize the skimmer with a sealing plate such as an AQUADOR. The use of such a plate allows you to keep the water level at a normal level which aids in keeping the winter cover up and prevents undue sagging.

[  ] Tighten the cable securely around cover.

[  ] Use Cover Clips to further secure cover. Another new product available to secure and seal the cover is with a roll of Pool Cover Wrap.   DO NOT HANG BOTTLES: Bottles hung from the cover will tear the cover!


[  ] Remove leaves and heavy debris that accumulate on cover

[  ] Remove excess water from top of cover (A submersible cover pumpworks best). Once the pool freezes, there's not much to do until everything thaws.

For owners of gunite or plaster finish pools: Please check with your local builder for any special instructions they may have.


ALL Chemical Winter Kits are made to properly WORK for a maximum of about 4 months. If the pool is going to be closed for a longer period of time (example closing before October 1 and opening after May 1), it is absolutely necessary to add additional shock and algaecide to the winterizing process. This will help to prevent not only algae growth but chlorine demand problems at pool opening.

A good closing and winterizing will provide you with a much simpler opening next spring.

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