How to Winterize Pool Plumbing (Blow Out the Lines)

This page is about the pipes. For water chemistry, covers and the full closing sequence, see how to close an inground pool or how to close an above-ground pool. Do the chemistry first, then come back here.

Do you need to blow out the lines at all?

Water left in a pipe turns to ice at 32 °F and expands. That can crack pipes, fittings and the pump housing. Whether you need to act depends on how often your area freezes.

Freeze risk by climate band (our grouping)

Where you live	What to do with the lines
Hard freezes every winter	Blow out and plug every line, drain all equipment, and cover the pool. Antifreeze is an extra step, not a replacement for blowing out lines.
A few freezing nights a year	The Florida Swimming Pool Association says to blow out the lines, plug them at the pool and add pool antifreeze if a freeze is a risk. It also says to run the pump or solar overnight during a freeze warning. One retailer guide says even one or two freeze events justify blowing out the lines.
Almost never freezes	Most guides skip the full blow-out. Keep the pump ready to run overnight if a freeze is forecast, and know where your drain plugs are.

We could not confirm a single temperature at which every maker says to start. Hayward's own closing guide gives no number for lines. Follow the manual for your pump and filter.

What you need

• An air source: a compressor, a blower made for pools, or the blower port of a shop vac. One retailer says a shop vac can stand in if its chamber is clean.
• Expansion (rubber) plugs for skimmers, and threaded or expansion plugs for the return fittings.
• A wrench and screwdriver for drain plugs, and a small container to keep the plugs in.
• Non-toxic pool antifreeze, only if your equipment maker and the antifreeze label allow it.

Match the method to your setup

Setup matrix

Your setup	Lines to blow out	Notes
Inground, one skimmer and returns	Skimmer line, then each return line	Lower the water until the return fittings sit above the surface.
Inground, skimmer and bottom (main) drain	Skimmer, returns, and the main drain line	Set valves so only the line you are blowing is open. Close each line after it is blown to keep water from backing in.
Inground with a cleaner line or extra returns	Every port that connects to the pool	Each port needs its own plug.
Above-ground	Usually none underground	Hayward says to disconnect the hoses and plug the wall outlets. Follow your pool manual.

Sources differ on the order of lines. One retailer starts with the skimmer line and then the returns and equipment, another starts with the returns. We do not think the order matters as much as these three rules: work one line at a time, blow until the stream is air with only a mist of water, and plug the line while air is still flowing.

Step by step

1. Do the water chemistry and cover plan first. Balance and shock the water, then lower it. Hayward says 12 to 18 in below the skimmer for a mesh cover, or 3 to 6 in below the tile for a solid cover. If the return fittings are still under water after that, one retailer advises draining the pool further so they sit above the surface.
2. Turn off power at the breaker. Then drain the pump, filter, heater and chlorinator using their drain plugs. Hayward says all water must be drained or blown out so equipment doesn't freeze and crack. Keep the plugs in the pump basket.
3. Remove the skimmer basket and drain the skimmer. Take out any water you can reach by hand or with a cup.
4. Set up the air source. Connect the blower or compressor hose to the line at the equipment pad. The exact connection depends on your plumbing, so check your manual. A shop vac must be on "blow", not "vacuum".
5. Blow the skimmer line. Open only that line, run air, and watch the skimmer. When water stops coming up and bubbles are mostly air, push in an expansion plug.
6. Blow each return line. Do the same at the return fitting. Plug the opening while air is still pushing, so no water can run back in. Repeat for every return.
7. Blow the main drain, if you have one. Open only that line. One retailer advises disconnecting the line, blowing it out, then closing the valve so water does not flow back in. Do this last, after the skimmer and returns are plugged.
8. Add antifreeze if you use it. Pool antifreeze goes in the skimmer and return lines, not the main drain, because the water there connects to the pool and thins the antifreeze. Use only the amount on the product label.
9. Cover the pool and store small parts. Keep the skimmer basket, drain plugs and fittings together in one labeled bag.

Compressor, blower or shop vac?

Pool guides name all three. The point is to move lots of air at modest pressure. We could not find a pressure number from a pool-equipment maker. A retailer's comment section mentions staying under 20 psi on a small compressor, but we treat that as one person's advice, not a rule. If you use a compressor, start at low pressure and check your pipe type, and ask a pool service if you are unsure.

A shop vac is the cheapest choice. Make sure the chamber is clean before you use it, as the retailer says, and that the hose fits snugly at the pipe so the air goes into the line and not into the room.

What not to put in the lines

• Automotive antifreeze. It is toxic. Retailer guides say to use only a non-toxic pool formula.
• Trapped water. A line that still has water in it when you plug it can freeze and split a fitting. Do not plug a line until air is the only thing coming out.
• Anything the equipment maker forbids. Some heaters and salt systems have their own winter steps. The manual overrides this page.

When to call a pool service

Hire help if you cannot trace which valve feeds which line, if the pipes run under a deck or are not accessible, or if your area gets hard freezes. A cracked line under concrete costs far more than a service visit.

In spring, remove the plugs, reconnect the pump and check for leaks before you start the pump. Our pool opening checklist and when to open and close a pool guide the rest. If your water level has dropped over winter, see pool water level.

FAQ

Can I winterize my pool without draining it?

Yes. You lower the water a few inches or feet, depending on your cover, but you do not drain the pool. Hayward says to lower it 12 to 18 in below the skimmer for a mesh cover or 3 to 6 in below the tile for a solid cover.

How do I winterize a pool with a bottom drain?

Blow out the skimmer and returns first, plug them, then blow the main drain with its own valve open and the others closed. One retailer advises closing the drain valve afterward so water cannot flow back.

Can I use a shop vac to blow out pool lines?

Yes, on "blow" with a clean chamber and a snug hose connection. Use a GFCI-protected outlet and keep the unit away from standing water.

Do I need antifreeze if I blow out the lines?

Not always. Hayward lists antifreeze as an alternative to blowing out and plugging the lines. Where freezes are a risk, the Florida Swimming Pool Association says to blow out the lines, plug them and add antifreeze. If you use it, it must be non-toxic pool antifreeze, never automotive.

Do pools in mild climates need blown lines?

If a freeze is forecast, yes. Without one, most guides skip it and rely on running the pump during a cold snap. We could not confirm a single temperature threshold.

Sources

• Hayward, Ten Essential Steps to Closing Your Pool (water level, drain plugs, blowing out lines, above-ground), read 2026-10-06: hayward.com
• Florida Swimming Pool Association, Winterizing in Florida (freeze protection steps), read 2026-10-06: fspa.com
• InyoPools, how to winterize a swimming pool (line order, plugs, antifreeze type), retailer guide, read 2026-10-06: inyopools.com
• PoolSupplies.com, how to winterize your pool's plumbing lines (main drain, antifreeze placement, skimmer plugs), retailer guide, read 2026-10-06: poolsupplies.com
• Simplified Pools, pool winterization in Texas (freeze events), retailer blog, read via search result 2026-10-06: simplifiedpools.com