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Pool Winterization

A guide for those closing their own pool.

*(or preparing for the closing of a pool by a pool service.)

General Goals :

  • Ensure the overall condition of the pool.
  • Protect circulation equipment from frost.
  • Cover pool
  • Storage of accessories

1. Ensure The Overall Condition of the Pool


If the pool is losing water into the winter months you may not be able to diagnose or repair the problem after the pool is closed.

If the pool is losing any noticeable water (¼”/day or more) make sure it’s not going to cause the winterized pool to drain unnecessarily. The water in a pool protects the base & foundation from frost damage.

Note the level after closing and be certain it’s not dropping.

Water Chemistry

Proper Water chemistry must be achieved in the weeks leading up to a pool closing. Chemicals cannot be added to a closed pool.

Leave the pool running and clean until the day you close the pool: A circulating Pool will remain cleaner and prevent frost damage just by having the water circulate through the equipment.

2. Protect Circulation Equipment From Frost

The expansion of water when it freezes & thaws will damage any piece of equipment in which it is trapped. Each part of the pool should be considered both separately and together when considering the best way of preventing frost damage.

Make sure you choose one of these:

  • Drain it or,
  • Get plumber’s antifreeze throughout it or,
  • Store it in a frost-free area

A General Approach To Protecting Circulation Equipment From Frost

A. Winter Water Level

Pump or siphon water out of the pool below the level of the return jets (about 14“ below the summer level). While doing this, give the filter a final backwash and the pool a final vacuum on waste.

B. Fixtures & Fittings Below The Winter Level

Fixtures & fittings below the winter water level need to be dealt with individually.

i) Main drain equalizer line :

When the main drain line is hooked to the base of the skimmer, insert a foam expansion rope down the main drain line and seal off the line with a plug & Teflon tape.

ii) Lights

Remove the light from the niche where it rests (leave sealed and attached to the wire) and force it to sink using a plastic bag and smooth round stones. Be certain the power is permanently off for the winter.

iii) Blow Out Lines
  • Remove eyeballs, suction grates, and baskets from the poolside of all fixtures.
  • Place the filter valve on recirculate and undo the drain plug on the tank.
  • Empty chemicals from any vessels attached to the pool plumbing – i.e. chlorinator.
  • Force as much water as possible out of the underground lines using an air blower, compressed air or a good wet/dry shop vac.

Blow from the equipment to the pool if possible. Tackle each line separately by sequentially turning valves, breaking open the system at valve unions, clamped fittings, or opening the pump.

Fittings connected to the same lines may have to be plugged and unplugged sequentially to clear the lines.

iv) Anti-Freeze

Force Plumbers Anti-freeze through each of the lines in the same manner by which you blew them out. Likewise, force anti-freeze through the pump, multiport valve, heater, and all of the circulation equipment.

v) Plug Off All Lines

Plug Off all lines with an appropriate expansion plug or threaded plug as needed.

vi) Drain Circulation Equipment

Follow the manufacturer’s recommendations to further ensure the protection of your equipment.

3. Cover the Pool

The goal of a cover is to maintain the water quality in the pool, to some degree, between closing & opening. A cover is not essential.

A. Tarp-style Winter Cover

Tarp-style covers are inexpensive to replace and are often the only effective way for a pool with waterfalls & waterside features to be effectively covered.

They are more prone to being caught by the wind. Water bags are placed end-to-end around the edge to create a seal on the uneven deck against wind and storms; they will then freeze solid where they sit.

Usually, several bags a year will need to be replaced. When a water bag falls into a pool it has smooth edges and generally floats due to the air trapped in it.

When alternate heavy items such as concrete blocks or slabs are used they do not seal as well and are prone to being blown in. When they do fall in with the cover they inevitably damage the pool.

Custom-made tarps are also available.

B. Lock-in Style Winter Cover

Lock-in covers consist of a fabrene or vinyl tarp custom-made to fit the pool.

Along the edge is a bead of vinyl that clips into an extra track in the coping. The step needs to be covered separately with a piece of tarp, board, or rigid cover. Usually, extra pieces of locking strip are needed to keep the cover in the track. However, this depends on the coping & bead.

C. Security Cover

A Heavy mesh cover is usually custom-made to fit each pool. Straps at 3′ to 5’ grid intervals each have a compression string at either end, which retains the tension on the cover.

Holes are drilled in the deck. Concrete is ideal, but they have been installed in both wood and interlock decks. A pop-up anchor is inserted at each hole and these thread flush for summer use.

A heavy snow load will cause the cover to sink & rest upon the water below. A steel bar is used to slide the tension springs onto the anchors.

D. Automatic Cover

Built-in covers activated by a switch require a perfectly rectangular track system which is either mounted on the deck or built into the pool and landscaping. A motor & cables cover & retract the pool as required.

Although expensive, this is the optimum in convenience and security.

4. Storage of Accessories

Solar blanket: cleaned and put away can also be washed with mildew-resistant cleansers; most are left on the roller and covered with an opaque piece of plastic.

Ladders: Should be cleaned and put away. All the small bits and pieces should be stored so that they’re easy to find come opening time.

Pressure gauges: Pressure gauges last longer if stored inside.

Iron Threads: Iron threads are best smeared with light grease to prevent rusting- i.e., diving board jig & iron heater header drain threads. However, you don’t want grease in the pool.

Heater: Turn off the gas valve in the heater as well as on the gas line. Mothballs or some other bug-rodent deterrent may assist in keeping the internal parts of a gas heater from harm.

Electric Power: Electric power to any equipment should be permanently disconnected to prevent accidental operation.

Automatic Cleaner: hose sections are better stored if separated, laid flat & straight.

5. Final Pre-Frost Check

Look out the window and make sure the water level hasn’t dropped and the cover has stayed on (more or less). Once it’s frozen there’s little to be done about either.