How to Drain a Pool

There’s more to draining a pool than pulling a plug or starting a siphon. If you do it wrong, you could damage your pool, yard, and even your neighbor’s property. These tips on how to drain a pool will help.

There are several times during the life of a pool where it might need a fresh start. Whether you need to drain it because of repairs or maintenance that can’t be done underwater or because the water quality has diminished beyond resolution, as pool draining is often necessary roughly every five years. And while draining a pool may seem like a simple concept, some pools — like fiberglass and vinyl — aren’t meant to be drained, so they require special consideration. There is a lot to know before you start.

Consult Your Local Water Authority First

If you just start siphoning water out of your pool with a garden hose, you could end up costing yourself a lot of time, money, and grief. Many municipalities have their own rules about how, when, and where someone can drain their pool, and you need to abide by those rules.

For instance, most municipalities will require you to run your pool water through your home’s sewer cleanout line so it will flow to a water treatment plant. Others might allow you to send all that water down the storm drains that line your street. Municipalities may also have water chemical composition regulations. Some may require the water to be chlorine neutral, which would necessitate a lot of chlorine neutralizer.

When to Drain a Pool

Some municipalities have rules about when you can drain your pool as well. In most cases, these time windows prevent streets and sewers from being flooded with pool water during typically rainy seasons.

There are other timing considerations as well. The heat of summer can blister and destroy a pool liner if it’s not submerged in water. The frozen ground of winter can push an empty pool upward, a situation known as “pool pop.” So before you begin, wait for a stretch of nice, dry weather in the spring or fall, when the water table is low and where daytime highs won’t exceed 85 degrees.

Tools and Materials

Fortunately, draining a pool doesn’t require much in the way of tools or materials. Here are the items you’ll need:

How to Drain an Above-Ground Pool

Draining an above-ground pool is relatively straightforward. Just follow these steps:

  1. Unplug the pool pump and any other electrical components so they can’t turn on.
  2. Attach enough garden hose to get from the pool to the drain point (sewer cleanout line, the road, downhill, or wherever else you’re legally allowed to discharge water).
  3. Attach the hose to the submersible pump and lower it into the pool.
  4. Plug the pump directly into the pool’s GFCI outlet (it’s best to avoid extension cords as they may separate and cause electrical hazards). The pump should be running.
  5. Check the end of the hose to ensure that the water’s flowing properly into the drain point.
  6. Check on the pool periodically.

Draining a pool can take up to 14 hours, depending on the size, so be sure to drain it on a day when you have sufficient free time. You need to be home to check on the pool, the hoses, and the pump frequently. Do not let the pump run dry or it can become damaged.

How to Drain an In-ground Pool

Draining an in-ground pool is much more involved than draining an above-ground one.

  1. Turn off or disable the pool pump, lights, auto-leveler, and any automatic timers. Many of these pieces of equipment are liquid-cooled, which means that if left on they will overheat as the water level drops.
  2. Attach enough garden hose to get from the pool to the drain point (sewer cleanout line, the road, downhill, or wherever else you’re legally allowed to discharge water).
  3. Attach the hose to the submersible pump and lower it into the deepest section of the pool.
  4. Plug the pump into the pool’s GFCI outlet (again, do not use extension cords). You should hear the pump running.
  5. Check the hose to make sure the water’s draining properly.
  6. Check on the pool periodically throughout the day.
  7. When the water level is low enough that the pump cannot expel any more water, use a hammer and screwdriver or chisel to break the plaster covering on the hydrostatic plugs.
  8. Using a large pair of pliers, unscrew the plugs and allow the groundwater to enter the pool. There can be quite a bit of flow and pressure, so don’t be alarmed. Also, the plugs are likely to become damaged, so be sure to have replacements on hand.
  9. Allow the pump to remove the groundwater.

Your in-ground pool may have two or three hydrostatic plugs. Removing all of them is best, but make the one in the deep end the priority. It will release that upward pressure the quickest, and you won’t have to fight running groundwater from the other plugs. Using this method, you should be able to avoid pool pop. Just be sure to replace the hydrostatic plugs before refilling.

By following these steps, you‘ll be able to avoid damaging your pool or flooding your yard or a neighbor’s. Once you finish your repairs or maintenance, you should have no problem filling your pool with fresh water for several more years of enjoyment.

Understanding “Pool Pop”

In the pool maintenance world, “pool pop” is a common term used to describe an unfortunate scenario where a pool owner drains their in-ground pool, only to have underground pressure heave the empty pool upward.

Pool pop typically happens when emptying an in-ground pool after a heavy, steady rain. The water and soil weigh more than the empty pool, so the ground “pops” the pool upward, causing lots of damage. It can also happen if you don’t drain the water far enough away, in which case you’re essentially the soil around the pool, creating enough hydrostatic pressure to the pool out of the ground.

To avoid pool pop, wait for a period of temperate, dry weather before beginning to drain the pool, and take advantage of the hydrostatic valves in its floor. Opening the plugs to these valves gives groundwater somewhere to escape. They’re typically covered under a layer of plaster, but they do remove easily.

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