Introduction

How you close your pool in October decides what you open to in April. Get it right and you pull the cover off clear water. Get it wrong and you're looking at a green swamp, or worse, a cracked pipe from water that froze where it shouldn't have.

This guide walks through closing your pool step by step, with the actual numbers to hit, in the order that protects both your water and your equipment over the winter.

Key Takeaways

• Close when water stays below 60°F consistently

• Balance the water 5 to 7 days before closing

• Blowing out the lines prevents frozen, cracked pipes

• Lower the water level below the skimmer

• A good close means an easy spring open

How to Close Your Pool for Winter

1. Wait for the Right Temperature

Don't close too early, because timing matters more than the calendar. The trigger is water temperature, not a date on the calendar.

• Close once water stays below 60°F

• Algae growth slows right down below 60°F

• Closing too warm invites a bloom under the cover

• In Northern Virginia that's usually mid to late October

Close while the water's still warm and algae keeps growing all winter under the cover. So wait for that consistent 60°F, even if the pool's done being used.

2. Deep Clean the Pool First

A pool going under a cover for 5 months needs to go under clean. Anything you leave behind sits and decays for the whole winter.

• Skim the surface completely

• Brush the walls, steps and waterline

• Vacuum the entire floor

• Empty both skimmer and pump baskets

Every leaf you leave behind feeds algae and stains the surface over winter. So 20 extra minutes now saves you hours of scrubbing in spring.

3. Balance the Water 5 to 7 Days Out

Get your chemistry right about a week before you close, not the day of. This gives the levels time to settle and circulate properly.

• pH between 7.2 and 7.6

• Total alkalinity between 80 and 120 ppm

• Calcium hardness between 200 and 400 ppm

• Balance 5 to 7 days before closing day

Balanced water over winter is what stops staining and protects your surfaces from corrosion or scaling. And correcting it a week out means it's actually settled by the time you cover up.

4. Shock, Then Wait

Shock the pool a few days before closing, then let the chlorine come back down. Covering a pool at shock levels can bleach color from a liner.

• Shock 2 to 3 days before you close

• Do it after sunset for full strength

• Let chlorine fall back to 1 to 3 ppm

• Add winter algaecide once it's dropped

Shocking clears out anything living in the water before it goes dark for months. But cover it too soon at high chlorine and you risk bleaching a vinyl liner.

5. Lower the Water Level

Drop the water below the skimmer, because water left in the skimmer freezes and cracks it. How far down depends on your cover type.

• Drop to 4 to 6 inches below the skimmer

• Use a mesh cover for a lower level

• Solid covers sit closer to normal level

• Don't drain the pool fully, ever

An empty pool can lift out of the ground or crack as it dries, which is a repair worth thousands. So lower it, but never fully drain it.

6. Blow Out and Plug the Lines

This is the step that prevents the expensive disaster. Water left in the plumbing freezes, expands, and cracks your pipes over winter.

• Blow the water out of all lines

• Plug the return jets with winter plugs

• Add pool antifreeze to the lines if needed

• Drain the pump, filter and heater fully

Never put regular car antifreeze anywhere near a pool, because it's toxic. Only ever use pool-rated antifreeze, and only in the lines, not the water.

7. Drain the Equipment

Your pump, filter and heater all hold water that has to come out. Anything left inside can freeze and crack the housing.

• Remove drain plugs from the pump and filter

• Store the plugs in the pump basket so they're not lost

• Backwash the filter before draining it

• Store any removable equipment indoors

A cracked pump housing from trapped water is a common spring surprise. So 10 minutes draining now saves a full replacement later.

8. Cover It Properly

Finally, get the cover on tight and secured. A loose cover lets debris, rain and light straight back in, which undoes everything above.

• Fit the cover snug with no gaps

• Use water bags or clips to secure the edges

• Consider a cover pump for solid covers

• Check it stays sealed after the first storm

On a solid cover, rain and melt pool on top all winter, so a cover pump keeps that weight off. And check it again after the first big storm to make sure nothing's shifted.

The Bottom Line

Closing a pool well comes down to timing and order: wait for 60°F, clean it, balance a week out, shock and drop the chlorine, lower the water, clear the lines, drain the equipment, and cover tight. Do that and spring is easy.

Closing is also the one job where a mistake costs the most, since a frozen line means a repair, not just a green pool. Paradise Pool Service handles pool closings across Fairfax, McLean, Arlington, Alexandria and Washington DC, with a free on site quote before any work starts. You can check coverage on the service area page.