by Rob Cox September 13, 2017
Originally posted 5 years ago, this popular post has been updated with even more tips!
Pool winterization is a careful chore. Do it incorrectly, and you could face expensive and frustrating freeze damage, cover damage or a green pool next spring.
For regions with temperatures that dip below freezing for days or weeks, or more than just an occasional overnight freeze, you have to winterize the pipes and equipment to protect them from freezing, which cracks pumps, filters and heaters, and pipes.
The pool water, stagnant without circulation and filtration, will also need your attention at closing time. Cleaning, Chemicals and Covering the pool will protect the water during winter, to give you an easier opening.
Here's some Top Tips that I came up with for winterizing an inground pool. If you have questions about closing your pool, click my name above and send me an email!
For solid pool covers, lower the water 4 inches below the skimmer, and for mesh safety covers (or solid safety covers with drain panels), go 9-12 inches below the skimmer, depending on how much winter rain and snow you receive. For safety covers, keep the water about 6" below the skimmer when a heavy snowfall occurs, to support the cover and prevent damage to the springs and straps.
To find out how much rain your city gets during winter, see this cool historical weather tool. Enter your zipcode on the first page, then select the custom tab to enter a date range. Most areas will receive more rain than the pool can hold. When you start to see the water level touch the cover, use a pump or siphon to lower the level down below the tile line.
To pump below the skimmer, close the skimmer valves, leaving the main drain open and either backwash or place valve on the 'Waste' setting. If the drain is not operational, or if you have a side by side (2 hole) combo skimmer, use a vacuum hose / head, to draw water from the pool, connected tightly to a hose adapter screwed into the skimmer hole. For Anthony pools or old style Sylvan pools that use a vertical diverter, plug the single skimmer hole at the top with a #10 plug, to pump from the main drain only.
After backwashing the filter, set a Multiport valve to 'Waste' to continue pumping the pool at a higher flow rate. If you have a DE filter, you can open the air bleeder, drain the tank and remove the filters for cleaning, while continuing to pump on the Waste setting. Sand filters can begin to drain, opening the air bleeder will speed draining of water inside the tank.
To lower pool water level by Siphon, attach the vacuum head to the pole and prime the vacuum hose fully, just like normal. Remove the head from the pole and place on a step or swimout area, or use a heavy item to hold the hose, so that it remains just 1-2 feet below the surface of the water. Cap the other end of the vac hose tightly with your palm, and holding the hose low to the ground, quickly walk the hose down to an elevation several feet lower than the other end of the hose. Release the hose end at ground level and it should start flowing, albeit slowly.
A Pool Cover Pump can also be used to lower pool water level, also albeit slowly. Small cover pumps can pump 300-500 gallons per hour. Larger pumps like the Water Wizard can pump up to 1200 gph and the APCP can pump up to 1700 gph. For perspective, a 20x40 pool has 500 gallons in each inch of water level. So, a pool cover pump will lower water level about 1" to 3" per hour, depending on size. Figure your total pool gallons with this cool tool - Pool Gallons Calculator.
Be careful where you pump, when lowering the pool water for winter. Dumping 5000 or 10000 gallons into one area can cause flooding and erosion and cause problems for plants and animals, or problems with neighbors. And please be sure that your water is well balanced, without very high sanitizer or algaecide levels, before you lower the pool level for winter.
Lowering the water will naturally lower the water in the pipes, and in some cases, some of the water will drain out of the return lines. Air is used to force water out of the pipes, and then the empty pipes are plugged at the pool.
Once the water has been pumped below the skimmer opening, if you have separate valves, you can open the skimmer valve slowly, to suck out the line. Be quick to close the valve before air sucked in at the skimmer reaches the pool pump, so you don't lose prime.
The G&G Mighty Vac was always my tool of choice for blowing the lines, but they've gotten so expensive, that we now supply the Air Supply Cyclone Blower to customers who want to blow their own pool pipes. In some cases, you can use a powerful shop vac to blow, or vacuum the water from the skimmer pipe, but need to be careful to blow out all of the water, and most Shop Vacs cannot blow out a main drain.
To blow out pool lines, attach the pool pipe blower hose to the skimmer with a hose adapter, and blow air backwards through the main drain, then close off the Jandy-type main drain valve, after it begins to bubble strongly. Then blow out any other skimmer lines, before sending air into the pump, filter, heater, chlorinator, etc, and back through the pool returns, spa jets and pool cleaner lines. The returns closest to the pump will begin to bubble first, then ones further away, after the closer wall returns are plugged. Plug returns and cleaner lines tightly while they are bubbling, to keep pool water from rushing back into the pipe. With a Cyclone type pool line blower, you can blow out all inground pool pipes and equipment from a single skimmer.
If you're not sure of the success of your line blowing you can add non-toxic pool antifreeze to the pipes. For the skimmer, just pour it in, it will flow to the lowest part of the pipe. For other lines, you can use a 5 foot piece of hose, connected to a large funnel. Insert the hose through the pump or a valve, and pour in the directed amount of pool antifreeze, so that it flows into the lines (pipes). You can't use antifreeze on a main drain line however, unless you dive down there and plug the drain, it will just flow into the pool, since it is heavier than water.
Main Drains are blown out and kept void by quickly closing off a positive sealing valve like the Jandy valve, while the blower is strongly running. If you don't have Jandy type valves on the main drain pipe, you can either not blow the pipe and wish for the best, or you can cut the pipe, install a double-union ball valve on the main drain pipe, just after it comes out of the ground. Or, just install this $25 Pentair 2-way Jandy-type valve on the main drain line.
After draining out the equipment fully (pump, filter, heater), replace drain plugs loosely, to prevent insects or small rodents from using your pool equipment as a winter home. Mint sachets or moth balls can be used inside of pool heaters, to prevent nesting rodents and birds.
Once the pool is clean, you should cover it as soon as possible. A clean pool will keep more of the winterizing chemicals in the water, and reward you with a faster and easier pool opening.
On a windy day, you can cover the pool immediately after cleaning the pool, pulling it open in certain areas for access to add winter chemicals and plugs for the return lines or pool cleaner line. When complete, button up the pool cover. If the weather is too windy and full of debris, waiting for calmer weather is a good choice.
For solid pool covers using water bags, lay them out around the pool, and drag the hose around to them. In cases where the hose is not long enough, line them up on a slight slope, insert the hose and let them fill without having to hold them.
To prevent damage to water bags, never drag the bag, or drop them from any height. To keep thirsty critters from poking holes in the bags and drinking from the fountain, set a few large bowls of water around the pool. Change the water every few weeks. Or just use Aqua Blocks. Holes in water bags can be patched with a vinyl patch kit, but Anderson's Leak Sealer does a better and easier job.
For safety cover anchors that won't come up, spray with WD-40 and move onto the next one. Some brass anchors need a little persuasion to raise up into winter position. See this blog post for tips on dealing with stickers and spinners. If you have tried and tried - but they still won't come up, it's OK to leave a few straps undone, but keep it less than 10% of the total straps.
If you have large, beautiful trees surrounding your pool, and they all end up in a slimy leaf soup on top of your pool cover - fight back with a Leaf Catcher. Just lay this on the cover when you close the pool, and a few months later when all the leaves have fallen, pull off all the leaves and twigs in under 1 minute. No exaggeration, it's so easy you'll wonder why you didn't do it years earlier.
For solid covers on freeform shape pools, fold the excess cover material underneath the cover, to act as additional padding around the edges, and to direct water away from the pool more efficiently. Leave a 2-3 foot overlap where possible, to keep the cover from stressing. For safety covers going over sharp coping or step edges, use carpet remnants as padding under the cover.
Bonus! Consider this post new and improved - now with double the amount of inground pool closing tips! Hope you learned something useful, but if you are still confused or concerned, hit my name at the top and send me an email about your pool winterization process.