What Happens if I Don’t Close My Pool for Winter?

what happens if i dont close my pool

If you closed your pool for the winter already, then we say congratulations…and sorry. Congrats for getting it done already, but sorry your summer is over! But if you haven’t closed your pool yet, and you’re still on the fence about doing so — this post is for you.

Closing your pool for winter is all about timing. If your local weatherman is already talking about upcoming cold fronts or frost warnings, you better get to it. We’re going to show you what happens if you live in an area with freezing temperatures, and you don’t close your pool for winter.

So buckle up and let’s dive into the damages and disasters that can arise from leaving your pool open all winter!

What Happens if I Don’t Close My Pool for Winter?

In short, it could fall apart. We know that sounds scary, but unfortunately, it’s true. There are endless potential problems that can result from not closing your pool correctly, some of which are catastrophic. Let’s get into the specifics.

1. Pipe Damage close your pool for winter to avoid pipe damage

Two of the most important steps for closing your pool for winter are lowering the water level to below the skimmer line, and ensuring that all water has been blown out of the pipes. Standing water left in the pipes and plumbing will freeze, and if you remember anything from your high school physics class, you know that water expands when it freezes. Frozen, expanding water will put tremendous pressure on equipment pipes, skimmers, and anything else full of water. Above ground pumps and pipes will freeze in less than an hour if temperatures are below freezing.

So again, one of the most important things to remember when closing your pool is to get all the water out of your pipes!

What About Underground Pipes?

Underground pipes do not freeze as quickly as above ground pipes due to the layer of protection from the ground. But that doesn’t mean they won’t freeze eventually. It takes several days of below freezing temperatures to freeze the ground and soil around the pipes.

2. Pump Damage

Pool pumps are expensive, that’s a fact! So taking care of yours, especially when you close your pool for winter, is in your best interest. It’s inexpensive and easy to replace frozen or broken PVC pipes and connectors, but it’s a whole other story to replace the full pump. To safely winterize your pool pump, remove the two pipe plugs from the connection points.

3. Heater Damage

And don’t think your pool heater is any stronger! Cast iron and polymer heater headers are usually the first thing to snap in a sudden freeze. Which is not actually a bad thing, as this forces the heater to drain and prevents greater damage. Winterize your pool heater by removing the front and rear header drain plugs, and disconnect the pressure switch inside the heater. Blow out the heater lines to remove any water left over.

4. Filter Damage close your pool for winter to avoid filter damage

Your pool filter tank can withstand enormous pressure, up to 50 psi in most cases, but that’s still no match for the power of expanding ice. In some cases, the tank itself will crack, or the clamp ring on cartridge or DE filters will crack in half, or the top mounted multiport valve flange will separate from the tank, or just start leaking, as shown here.

To winterize a pool filter, open the air bleeder and remove the filter drain cap or drain plug. If you have a multiport valve, turn the handle to a spot between any two positions. And if you have a push-pull slide valve, place it mid-way between the up and down positions.

5. Deck Damage

Nothing will ruin your spring pool opening like discovering a pipe leak underneath your pool deck. Improper pool closing practices can cause a major headache in the form of a spring time pool deck gut-job. Fixing external, above ground pipes is not much of a challenge, but having to cut through thick concrete or stone deck to fix underground pipes is another story.

6. Pool Walls and Structure Damage close your pool for winter to avoid pool wall damage

If you have an above ground pool, there’s something unique that can happen if you don’t properly close your pool for winter and use an air pillow or winterize the skimmer properly — they can crumple like tin cans. An above ground pool is designed to contain water inside, but as an ice sheet thickens across the pool, it puts outward stress on the walls. When the ice sheet is also frozen inside the skimmer – any heaving, tilting or slipping of the ice sheet can wreak havoc on even the strongest above ground pools.


Still Don’t Want to Close Your Pool for Winter?

In The Swim carries the pool-saving Intermatic freeze sensor, which is compatible with the PE153 Digital Timeclock. This setup allows you to pre-set a temperature for the pump to turn on automatically, so you don’t have to worry about it.

If you do close your pool for winter, don’t forget air pillows and skimmer plugs to protect your pool. And for inground pools, new winter pool plugs and pool cover supplies are available. And every well-winterized pool can find a cheap insurance policy in pool antifreeze.

If it’s too late to close your pool for winter, and if your pool equipment is already frozen, remove the drain plugs, throw heavy blankets or tarps over the equipment, and set up a small space heater with plenty of ventilation, you don’t want it to catch on fire next!


How to Prepare Your Pool for Freezing Temperatures…

  • Keep the pump(s) running! 24/7 when temps threaten to dip below 32° F.
  • Maintain a clean filter and pump basket to ensure proper flow rates.
  • Check that all valves are open; no fully closed valves in/out of the system.
  • Check timeclock or programs, remove off trippers or override programs.
  • Power outage? Quickly remove all drain plugs and open air bleeder on filter.

Power Shut Off and it’s Below Freezing…

  • Shut off power at the circuit breaker.
  • Remove drain plugs – from pump (2), filter (1), heater (2), chlorinator (1), etc.
  • Open filter air bleeder to assist in faster drain down.
  • Cover entire system in heavy blankets and tarps.
  • Make a ‘skimmer bottle’ with antifreeze, or a Skimmer Gizmo to absorb ice expansion.
  • Pool Antifreeze can be added to pipes, if power remains off. Use 1 gallon per 10 feet of pipe.

Your Pool Has Freeze Protection…

  • Monitor the system for failure; make sure that it is operating properly.
  • Be sure All valves are open; skimmers, drains, vacuum, returns, spa jets, fountains.
  • Keep children and pets safely indoors.

Pool Surface is Frozen Solid…

  • Monitor the system for failure, make sure it is operating properly.
  • Monitor the water level. If your pool has a leak, add water to support an ice sheet.
  • Be sure all valves are open; skimmers, drains, vacuum; returns, spa jets, fountains.
  • Keep children and pets safely indoors. No walking or playing with the ice sheet.
  • Do not attempt to break the ice sheet, or melt the ice sheet. Do not add hot water.
  • Ice sheets grow slowly, about 1/4″ per day in most cases.
  • Ice sheets of over 2″ exert considerable outward pressure.

Can You Run Your Pool Cleaner During Freezing Temps?

  • Pool Cleaners can be operated during freezing temps if needed.
  • Do not operate a cleaner if the pool surface is frozen over, or in icy conditions.
  • Drain the pool cleaner fully after use in cold temps. Store indoors if possible.

Should You Use an Automatic Cover During Freezing Temps?

  • Automatic covers are best not opened when the pool surface is frozen.
  • Covering the pool may not prevent it from freezing over, but will slow the process.
  • Keep the cover pump off, to avoid an ice sheet on top of the cover.

Can You Use a Variable-Speed Pump During Freezing Temps?

  • In most cases, low speed is sufficient, but use medium just in case.
  • Be sure that all lines to and from the pool are open, and water is moving.
  • Override any programming for less than 24 hours per day. Run VS Pumps 24/7.

Will a Salt Pool Freeze?

  • Salt pools will freeze just like any pool, although it has a slightly lower freezing point.
  • Salt in a saltwater pool will not protect pool equipment or pipes from freeze damage.

Your Pool is Frozen and Leaking…

  • Add water to maintain level, to support the heavy ice sheet.
  • Ice sheets can fall at angles that damage pool liners, lights, ladders, or wall fittings.
  • Ice sheets grow slowly, about 1/4″ per day in most cases.

For those on the fence, you should seriously consider going the pool closing route. Now is the time to do it, and if budget is an issue, In The Swim offers some nice winter covers, along with pool winter kits.

17 thoughts on “What Happens if I Don’t Close My Pool for Winter?

  1. We had a fiberglass pool installed in October. The cantilever concrete coping was poured October 17. My concrete installer is saying wait 28 days before closing the pool and drilling the anchors for the loop loc cover. We have some below freezing nights coming in the coming days. Can I run my pump during the night with the temperature in the 20’s and be safe? Daytime temps should be high 30’s and 40’s.

    • HI Jeff, sure thing no problem, just be sure that the timeclock won’t shut off the pump during the night (remove the OFF trippers), and be prepared for any rare power outages that may foil the plan. If so, run out to the equipment pad and remove the drain plugs on the pump, filter and heater, etc – all the above ground equipment. Also, be sure that all valves are open, to and from the pool, just cracked a bit is fine, so that water is flowing through all pipes. as long as the water is moving it won’t freeze, even in below freezing temps.

  2. Disconnected hoses from the pool and bringing filter and pump indoors water is drained below skimmer. Did not add any chemicals to pool for winter. I have a pillow and a cover on pool. Will pool freeze since I did not add any chemicals? Is it ok as is.

    • Hi Mag, yes the pool will freeze, the winter chemicals don’t prevent that – they are more for algae control and stain prevention. Since the water is already cold and assuming the (solid) cover is in good shape without any holes – you could skip the chemicals this year, but only if you open a few weeks early. If you plan to delay opening, or is spring is really warm, open up the cover and pour in a bottle of Algaecide 60 Plus, then cover the pool tightly again until ready to open.

  3. Sharon Radecki

    I live in nw Pennsylvania. Planning on getting new liner in spring. Do I need to cover pool? I will be taking filter in garage for winter. Thank you

    • Hi Sharon, good question. Since you will be draining the pool and replacing the liner, do you need a winter cover? Well, not to protect the water, and not to protect the liner, but for the walls… a solid ice sheet allowed to grow thick, expands to put pressure on the walls. Air Pillows are normally used, under a cover, to prevent a solid ice sheet from forming. Without a cover, you could string together 1-gal milk or or water jugs, or 2-L soda bottles, with some pea gravel and a bit of pool antifreeze, to run across the pool, so they are 1/3 – 1/2 submerged – to absorb the ice expansion, and prevent a solid and very thick ice sheet from forming.

  4. Latoya Green

    I didn’t get around to covering our above ground pool. It was closed cleaned and disconnected from the pump, just uncovered. I have made sure the kids would go out and do a bit of brushing and removing leaves and then we had to leave town unexpectedly. The pool looks frozen solid. It’s been this way for about 2 weeks an will probably be another week or 2 befor our temps go above 32. What’s the best thing for me to do at this point?

    • Davy Merino

      Hi, without an air pillow, aboveground pools can freeze solid, and this puts pressure on the pool walls, so is best avoided. You can bust thru the ice carefully if it is thin, and place several 6-12 gallon milk or water jugs with a few inches of pea gravel inside, to float in the pool, and absorb ice expansion, or keep the pool from freezing solid across. If you want to try to melt the ice, if it was only an inch or so thick, you could maybe use a heating cable…? If it is several inches thick, I’m not sure what you can do, maybe a floating pond heater, or just wait and hope for no damage…? If you try to bust up a thick ice sheet, it can easily shift, and cause the damage you are trying to avoid.

  5. We weren’t able to close/wonterize our inground pool. We had a family emergency that required us to tend to our baby. t’s been below freezing for a few days and the pool is frozen. It looks like the pump and stuff is also frozen. We have a pool heater. All have been turned off for a few weeks. We’re trying to get a company to come close it immediately (if possible). Should I take a heater out to try to thaw the equipment and turn it on along with the heater? Did we ruin our pool, pipes, equipment? 🙁

    • Davy Merino

      Hi Tara;

      If you find your pool equipment frozen, the first thing to do is cover with heavy woolen blankets, and place a small space heater, and remove the drain plugs on the pump(s), filter, heater, chlorinator, to drain all of the aboveground equipment. In your case, and in most cases like this, one or more parts of the equipment may have frozen and cracked. Usually the pool heater header will crack first, and this relieves the pressure, and allows some water to drain. In more severe cases, inline valves or the pump may crack. You should be able to see most cracking, if you inspect your aboveground equipment and pipes closely, but heater damage is sometimes harder to see. The pipes underground are likely OK, without damage. In most cases like this, you can expect repair costs in the $500-$1500 range. Not too bad, I hope. Good Luck!

  6. Judy H Gates, NC

    I plan to leave my pool open all winter in NENC. I will leave the pump running 24/7 just like I do in pool season. I hope for the best, we have never been 32 degrees below zero. I figure with the pump running, I should be ok…..

    • Davy Merino

      Hi Judy, I hope i didn’t say 32 degrees below zero! At 32°, or lower, pipes and pumps could freeze, if the water is not moving thru the pipes. In NE NC, you will get some below freezing temps, but as long as the pump is running, and all the pipes are open (no closed valves), the water won’t freeze, and you’ll have no problems. The pool surface may freeze, but that should not be a problem, again as long as the pump is running, it won’t freeze very thick-ly. The one big worry you may have is a power outage, or pump motor failure. In both cases, if temps are below 32°, remove the filter and pump drain plugs as fast as you can, and throw a heavy blanket(s) over the filter system, maybe place a small space heater if needed, if you have power.

  7. I always drain in ground pool pipes, shop vac or blow out the water and add at least 1.5 gallons of the pink RV antifreeze and plug up the the pool side inlets to prevent water from entering the return and skimmer pipes as the winter rain and snow melt refill your pool. for the bottom drains pour 2 gallon of the antifreeze into the pump side pipes until you see some pink come out of the bottom drains. The pink antifreeze is non toxic never use the green version in you pool or allow it to drain on the ground. (or use pool antifreeze – editor)

  8. Arthur J Spina

    Hi what are your thoughts about winterizing the plumbing but keeping the pool uncovered. I have an inground on long island NY. What are the risks assuming I rake and swirl in chemicals every so often?

    Thank you for your input
    Artie

    • Hi Arthur, sure you can do that! The main risk is staining from excessive leaves and such just sitting on the pool floor. But, if you are able to clean the pool every few weeks, and you don’t mind using extra chemicals (fall and spring – cleaning or chemicals many not be needed Nov-Feb), you’ll be fine. Here’s a related blog post from another well respected blogger on another well respected pool blog. 🙂 Can I Keep my Pool Uncovered all Winter?

  9. David Franskevicz

    Living in the northeast, how do I keep my winter cover on my above ground 16 x 36 pool from blowing up all over? 50% of my pool is surrounded by a deck. Doesn’t take long for it to become wind damaged.

    • Davy Merino

      Hi David, there are 3 products to prevent wind problems on aboveground pool covers. Cover Seal, like a giant roll of saran wrap, no go in your case. Cover Clips, used every 2 ft or so, to clip the cover to the pool top rail, and also Wall bags, placed on the inside edge of the cover, or run thru the cable, to provide more support. For the part that is surrounded by deck, I would also think cover clips. there is another one too, called cover cliploc jr., which we don’t carry. So, essentially, clip the cover to the pool, and or weigh down the cover edge, or put weights on the cable, and have a tight cable. Also, a little bit of water left on the surface, just 1/4″ to 1/2″ across the surface, can help hold down the cover.

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