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Pool Winterizing

We also teach an expanded version of this, with photographs and extensive notes, in our Pool School classes on Pool Closing.

NOTE:  The best way to close your pool is to take your time.  Do a little bit every day for 3-4 days, or take two weekends.  Don’t close too early-wait until the water temperature drops under 50°F.  If the weather turns warm and the water heats up, the Winter Kit chemicals still may not be able to prevent algae growth.  Pools with bolt-on mesh safety covers should be closed very late in the year (November) and opened very early (April).

At least one week before you close, perform a bucket test to make sure your pool is not leaking.  Put a weighted bucket of  pool water into the pool; on the top step, or tied to a ladder or something.  Make the water level in the bucket exactly the same as the water level in the pool.  Don’t use a liquid or solid solar cover in the pool unless you use it in the bucket too.  Now they will evaporate at the same rate, and they will get the same amount of rain.  If the pool water gets lower than the bucket, you have a leak.  If the bucket water gets lower, try it again.  If you have a leak, find it and fix it before you close.

A.        The Pool

1.  Solve Problems First.  You have to start with clear, algae-free water; with normal pH sanitizer, algicide levels.  If there is anything wrong, like algae or cloudy water, get our Pool Tips™ on that, and fix the problem first.

2.  Testing.  Up to three weeks before closing, bring in a pint of water, and ask for a winter balance test – it’s not the same as a summer balance.  Follow the balancing directions on your print out (if necessary), and bring your sanitizer and pH levels into normal ranges.

3.  Housekeeping.    A week before closing, brush the walls to loosen up any algae, slime, or water mold.  This is very important.  If the pool is not perfectly clear and clean when you close it, the pool will probably turn dark green over the winter.  Skim everything off the top, and vacuum or scoop all leaves and debris off the bottom.  Do it again the day before closing.

4.  Chemicals.  At least two weeks before closing, stop re-filling your automatic chlorinator or brominator, so that you completely run out of chlorine or bromine before closing.  Once you run out, switch to Dichlor chlorinating granules mixed in water and put directly into the pool.  You do not want to have any chlorine tables left in contact with the water when you close.

The day before closing, shock or oxidize the pool with your normal initial dose.  If your shock or oxidizer has two doses on the label, use the larger one.  Do not use potassium monopersulfate to shock for closing.  It’s a perfectly reasonable oxidizer, but it won’t kill anything.  Six to 24 hours before closing, add a good non-chlorine winter kit, being careful not to use a kit with winter chlorine tablets that could break, settle to the bottom, and ruin your liner or pool bottom.  Those kits are made for the South, where pools do not freeze, and generally do  not have vinyl liners.

Allow the water to circulate 24 hours after the shock or oxidizer, to allow the chemicals to circulate, and the chlorine level (if you used a chlorine shock) to return to normal.  A high chlorine level can shorten the life of your cover.  You only need six hours for the winter kit to circulate.  Twenty-four is OK if it’s convenient, but not necessary.

Gunite and plaster pools must get extraordinary care in winterizing.  High mineral counts can stain the walls over the winter.  Unbalanced water can cause etching or calcium deposits on the walls.  Be sure to add Winter Anti-Stain, and balance all factors carefully; best done at least 48 hours before the shock or oxidizer.

5.  The Skimmer.  On inground pools, guess how much it will rain this winter, and lower the water level that far below the bottom of the skimmer:  probably six to eight inches below.  The easiest method is by vacuuming to waste or bypass (not backwash).  When the water gets to the bottom of the skimmer, switch to just draining with the main drain.  If you don’t know how, ask us.  If you have a safety cover, follow the cover directions.  It will probably be 15” to 18” below the deck.  Not following those directions can be dangerous… and destroy the cover.  Screw a Skimmer Saver into the skimmer to absorb ice expansion while keeping water out of the lines.

On above-ground pools, cover the front of the thru-wall skimmer with a stainless steel faceplate to prevent ice damage to the skimmer.  This also allows you to conserve water.  Remove the hoses, and wedge an empty, capped plastic quart bottle into the skimmer to absorb ice expansion.  However, leave the bottom of the skimmer open, to allow water that does get into it, to escape.

On all in-ground pools, and above-ground pools with a winter plate; plug the returns with a threaded plug (the best) or an expansion plug (second best).  We carry twelve sizes.  It would be helpful if you knew the brand, model, or size before you came in.

However, if you did not use a winter plate on the above-ground skimmer, don’t plug the return or you can destroy the pool.  Very Important!  Both the skimmer and return need to be open, or they both need plates blocking the water from inside the pool.  You can not leave one open and the other closed.

6.   The Lines.  Remove all above-ground lines, and store someplace that will not freeze.  Blow out all under-ground lines with a compressor.  It will require at least a one horsepower motor, a large holding tank, and be capable of 80 PSI.  You can rent ours; with directions and lots of tools and attachments to make it easy.  One at a time, remove the return plugs until the line bubbles all air and no water.  Follow the order of the underground lines:  from shortest distance to farthest.  Then, re-plug.  This is a two-person job.  To be on the safe side, pour swimming pool antifreeze (not automotive or R.V.) into the lines and blow again until it comes out the other side.  Make sure it’s compatible with the chemicals that will be in the pool next spring.

This is all very important.  If your lines or filter freeze, they could easily break, causing very expensive damage (like digging up the deck).  Always follow the pool builder’s or manufacturer’s instructions, especially if they conflict with ours.  We are not accepting liability for $10,000 deck repairs when we give out free advice!

7.  Leaks.  If you did not do a bucket test right before closing, mark the water line on the wall or skimmer plate with a pencil.  Check the water level twice a week for at least a  month.  If the water level drops, call us immediately.  If the  water leaks out from under a bed of ice, the pool could be destroyed.  If a gunite pool completely empties, it may pop out of the ground.  If a metal or plastic-walled in-ground pool empties to less than one foot in the shallow end, the walls could bend or cave in.

B.         The Equipment

1.    The Filter Tank.  Backwash or drain the tank.  If you have a sand filter, throw away the sand.  We  recommend that you replace the sand every year, and at least every three years.  If you have a cartridge or DE (Diatomaceous Earth) filter, wash the elements with a good filter cleaner that is compatible with your pool chemicals.  Also, use a filter cleaner if you are not replacing the sand.  We’ll be happy to show you how.

2.    The Pump.  If you like to use pump protector, go ahead.  However, there is no possible use for it in any normal swimming pool pump.  If it doesn’t rust during a summer of chlorine and water, it’s not going to rust in a winter of air.

3.     Freeze Protection.  Our best advice is to put everything someplace warm – like the cellar.  If you have to leave anything that normally holds water where the temperature will drop below freezing, please check the manufacturer’s directions.  The greatest danger is generally to the filter tank, pump, heater, salt-to-chlorine generator, or automatic chlorinator.  You will probably be opening freeze plugs at the very bottom of the unit, and adding swimming pool antifreeze.  You were supposed to have run out of chlorine or bromine tablets by now.  If not, remove partially dissolved chlorine or bromine tablets (be careful) and store carefully in a clean, dry, plastic bag, then put the bag in a child-proof container.  Copy the safety warnings from the original container and  mount them on the new container.  Don’t put them back in a container with other chlorine.  However, don’t leave them in the chlorinator or brominator if it’s hooked up to anything.  The  chemicals could ruin everything near them – especially the heater.  Obviously, never put any chemicals, including antifreeze into an automatic chlorinator.

4.   Valves and Fittings.  Any rubber fitting, o-ring or gasket that’s easy to get to should be covered with O-Ring Lube to keep them from drying out.  Avoid Vaseline, or anything with petroleum distillates that will break down the rubber or plastic.  Cover the valves, unions, and fittings with cloth or plastic loosely held on by rubber bands.  Keep the valves partially open.  Your goal here is to keep water, snow, and chipmunks out (of course, you’d never have mice or rats), but to allow air in.  If you seal out the air, you could pop off the plugs inside the pool if the air barometric pressure changes over the winter.  The only exception here would be the main drain line if you were trying to maintain an air lock.  Since there’s no plug inside the pool, the water itself will cushion the pressure changes.

5.   Other Equipment.  Remove safety lines, ladders, portable stairs, underwater lights, automatic pool cleaners, and anything else that could be broken by ice or forced by the ice to hurt the pool’s surface.  Remove the salt-to-chlorine generator cell.  If you have a spacer, put that in its space.  If not, you will have to blow out the lines up to the space, then start again after it.  Antifreeze could be bad for the cell’s platinum electrodes.  Clean the cell according to the manufacturer’s directions or let us do it for you.  Cell cleaner is safer and easier to use than muriatic acid. 

C.        The Cover

1.   The Ice Equalizer.  Most above-ground and a few in-ground pools should get one or more ice equalizers (pillows).  While they are not always mandatory to maintain the pool’s warranty, they are an inexpensive insurance to keep ice pressure off the walls.  Too many pillows are bad for the cover.  Too few are bad for the pool.  We can help you determine the right amount.

In any case, blow up the ice pillows with a vacuum cleaner exhaust or an electric pump (we carry them) at least 48 hours before you need them.  Put a  weight on them and store overnight to make sure that they’re not leaking before you put them in the pool.  Then open the valve and let out about 10% of the air, so that the equalizer is a little soft.   Tape the air valve shut with duct tape, or a waterproof tape.  Set the valve down into the water, when you put them into the pool.

Tie them loosely in the center, with light string.  The theory here is that the cover should not break the string when it sinks into the water, but the string should break before the pillow breaks.  Ultimately, the pillow will break – they generally only last one or two winters.  Remember, it’s better to have the pillow break, than the pool wall.

2.  The Cover.  Flip or float the cover out over the pool.  Often, it’s easiest to tie a string to one side, to help pull it across.  Covering a pool is always easier with two people.

The entire cover must touch the water, except only where it goes over the pillows.  When the cover is on, you must be able to run your hand down the wall of the pool, to the water.  If the cover is too small (or the water level is too low), the cover will stretch out on an angle from the top rail to the water.  This is Dangerous.  If the cover is too tight, the weight of snow or rain could tear the cover (if you’re lucky) or pull in the top rails (if you’re not).  If you are not sure, call us for advice.  Above-ground covers are best held on by a steel cable and winch under the top rails.  In-ground covers are bolted on, or use water tubes (filled only 2/3 full, for ice expansion), running bumper to bumper around the edge so that leaves, dirt, and animals do not get under.  On ground pools and above-ground pools with decks usually use some combination of cable and tubes.  Ask us how.

Bolt-on safety covers allow light, air, and algae to get into the pool, all winter and spring.  You need to close those pools very late, open them very early, and use a special algaecide that won’t hurt the cover, for two to four months during the off-season.

When you’re done, run a little water on top of the cover to keep it from blowing in the wind.  However, as the water level builds from rain and melting snow, pump or siphon it off.  Once the pool freezes, though, leave it alone until it melts.

Note:    If you are a new owner of an in-ground pool, we recommend that you hire the original builder (if possible) or a qualified service person the first time you close it, to show you the intricacies of your particular pool.  We’ll be happy to refer you to someone. 

Shopping List

___ Pool Cover                                          ___ Cover Stakes
___ Expansion Plug                                 ___ Cable Winch
___ Cover Pump                                       ___ Cover Cable
___ Anti-Stain                                           ___ Wall Brush
___ Water Tubes                                      ___ Cover Cleaner
___ Ice Equalizer                                      ___ Cover Repair Kit
___ Shock                                                ___ Leaf Sweep
___ Winterizer                                          ___ Skimmer Plate
___ Winter Kit                                          ___ Cell Cleaner
___ Pool Antifreeze                                 ___ Skimmer Saver
___ Leaf Rake                                         ___ Winter Sheen

Revised:  7/30/12

We write Pool Tips for the exclusive use of our own local customers.  They are meant as a summary of general information, to be discussed in our store, with our staff, to determine which items are best for specific pools.  Pool Tipsare a trademark of Gull Group, Inc. All rights reserved.

Our suggestions assume that you have given us a proper description of your pool’s size, history and symptoms.  Sometimes we can figure it out, sometimes we can’t.  Your doctor has years more training, far better diagnostic tools, and makes way more money—and sometimes he or she gets it wrong, too.

  1. Read all labels carefully, and only use chemicals exactly as described on the label. Never mix chemicals together outside of the pool. Some of them can cause a fire or explosion.
  2. Do Not follow any advice or suggestions here without coming into the store, customizing them to your specifics, and receiving them in writing.
  3. Do Not print these out or reproduce for any purpose whatever. They are all copyrighted, and we take our copyrights very seriously.
  4. Don’t Blame Us for anything. It’s free advice, and worth the price paid. We’re trying to help, but pools are complex, and chemicals and electricity are dangerous.
  5. Our Best Advice: Go find a local pool dealer who knows what they are doing, become a steady customer, and give them a chance to learn about you and your pool. Pick a brand, pick a store, and stay with them.