How To Drain Your Pool (And Why You Should)

Kenneth Wilson

After learning how to shock my pool, I found out that it’s also important to drain it. Even if you properly maintain your pool, balance the water chemistry, and clean it with chemicals and tools, the time will come that you need to drain and start with new water.

Once again, I am faced with a pool task that I have no knowledge about. But since this is another process that both old and new pool owners should know how to do, I learned it. Luckily, you don’t have to do it often, unlike pool shocking. 

I’ll help you out and share with you how to drain your pool, why it’s important to drain it, and answer some frequently asked questions about this topic.

Why should you drain your pool?

Aside from replacing the pool water after years of using it or there’s a severe algae contamination, here are other reasons why it’s important to drain your pool.

Total Dissolved Solids or TDS build-up: After a few years, when TDS, or the material that cannot be filtered out anymore, is more than 2,500 parts per million, it would be difficult to balance your pool water’s chemistry. It’s not unsafe, but you would be spending more on chemicals. Aside from the cost, this can also cause the surface of your pool to deteriorate.

Maintenance: When your pool has high water, which often happens after days of heavy rainfall, it may heave out of the ground. Drain only half and then refill it on the same day. You should also drain your pool when you need to rebalance the chemicals or when you see mineral stains on the bottom and sides of your pool.

High Cyanuric Acid: It's time to drain the pool when the cyanuric acid is between 100 to 150 parts per million.

A hurricane or tropical storm is approaching: You need to partially drain your pool to avoid it from overflowing from heavy rainfall.

Repairs or upgrades: Resurfacing, doing a chlorine bath, removing heavy stains, replacing the liner, repainting, and doing acid washes.

Before you start draining the pool, make sure the pump, automatic timer, or filter is off. Don’t forget to turn the pool light off because it can overheat without the water. You should also wait for chemicals to dissipate before draining.

It’s important to remember these as well as to follow the proper steps of draining so you don’t flood your home or neighbors, destroy your lawn, ruin the pump and other equipment, damage the pool liner, or pop the pool (see video below). 

How to drain your pool

So now that you’re ready to drain, here’s how based on what type of pool you have.

There are two types of in-ground pool, concrete and vinyl, which will need to be drained differently.

For Concrete In-ground Pool

A concrete in-ground pool is one of the hardest pools to drain because if done wrongly, the pool can pop out (as seen in the video above). You might want to drain your pool after days of heavy rain, but it's best not to. Aside from the pool water level increase, the groundwater can also make the pool heave out.

Here’s how you can drain your concrete in-ground pool.

Step 1. Locate the hydrostatic valve in the main floor drain. If you don’t have one, you should get a professional to drain your pool.

Step 2. Rent or buy a sump pump and then attach a hose to it. Place it at the deepest part of your pool and then turn the pump on.

Note: Make sure that the other end of the hose is draining into a place that is fine with your local regulations.

Step 3. Keep an eye when draining this type of pool. Check if it’s draining properly, if the hydrostatic valve is still working, and make sure not to leave it empty for a long period.

For Vinyl-lined In-ground Pools

If concrete pools are prone to popping out, then vinyl-lined pools are more prone to tearing or ripping. The steps to properly drain it is almost similar to the concrete one. See the steps below.

Step 1. Rent or buy a sump pump and connect it to the sewer access point. Place the pump at the other end of the pool.

Step 2. Plug in the pump and turn it on.

Note: If you’re planning to repair or replace parts of your vinyl-pool, do it immediately and quickly after emptying the pool. If it’s empty for too long, the vinyl will dry up or crack from the heat or sun, which may damage the entire pool.

In-ground Pool with Main Drain

If your in-ground pool has a main drain made for draining, you can use it to drain your pool instead of following the steps mentioned. 

In this case, the valve should have three suction settings: skimmer, main drain, and off. Turn the system on before starting the suction process. The filter should also be in drain or backwash mode. Make sure that the other end of the backwash hose is draining into a place that is fine with your local regulations. Once everything is set, turn on the pump.

For Above Ground Pools

There are two ways you can drain your above ground pool.

First is the pumping method, which is the more recommended one. 

Step 1. Get a submersible pump. Choose one depending on the price and how much water you want drained per hour.

Step 2. Connect it to an extension cord and then put the pump in the water. Don’t forget to attach the output house and place the other end at a place that is approved by your local regulations.

Step 3. Turn it on once everything is set. Check the process when you can to see if the water is properly draining.

The second method is siphoning and all you will need is a garden hose. You should only do this method if you don’t have a submersible pump or the budget for it.

Place one end of the garden hose in the pool and then fill it with water. For the other end, make sure it is below the pool level. Don’t let air bubbles inside the hose to make it work.

Note: The length of the hose should be longer on the side that the water is going down. Adjust it as the water level of your pool goes down.

DO NOT use the drain plug to remove water from your above ground pool. This will flood the ground under your pool which will create a sinkhole or ditch. This will damage your pool liner and eventually, your entire pool.

DO NOT slash the liner to drain your above ground pool. It’s wrong and a slow process.

Using filters to drain your pool

Another method you can use to drain your pool is using your filter system.

Step 1. Get a backwash hose with clamp and attach it to your filter.

Step 2. Place the other end of the backwash hose and let the water drain into a place that is allowed by your local regulations.

Step 3. Turn off or unplug your pool filter then set it to backwash. Plug it in or turn it on again.

Step 4. Let it backwash for one minute, then turn off the filter again.

Step 5. Change the filter setting to waste and then shut off the skimmer.

Step 6. Open the main drain and turn the filter on.

Note: If you are closing your pool, drain the water until it is four inches below the skimmer.

This process differs if you have a sand filter, cartridge filter, or diatomaceous earth (DE) filter.

Cartridge Filter

If you have a cartridge filter, there are two different draining methods.

  1. Drain Valve

Step 1. Check if your filter system has a valve between the filter and pump.

Step 2. Turn off the pump and then turn the valve until it blocks the water going into the filter.

Note: Remember the original position of your valve.

Step 3. If you did this correctly, the water should start coming out of the opening once you turn the pump on.

Step 4. When you reach your desired water level, shut the pump off and rotate the valve back to its original position.

  1. Drain Plug

Step 1. Shut the pump off and unscrew the drain plug at the back off the filter

Step 2. Turn on the pump and let it drain until it reaches your target water level.

Step 3. Once you’re done, turn the pump off and MAKE SURE to put back the drain plug at its proper place. 

Sand Filter

Here are the steps to drain your water using a sand filter.

Step 1. Shut the pump off.

Step 2. Place the other end of the backwash hose to a place that is approved by your local regulations. 

Step 3. Turn the multiport valve (found at the top or side of the filter) clockwise to the waste setting. 

Step 4. Turn on the pump until you reach the desired water level.

Step 5. Make sure to turn off your pump before returning the multiport valve to its original or filter setting.

Diatomaceous Earth or DE Filter

You can also drain your pool using a diatomaceous earth or DE Filter.

Step 1. Manually turn off the pump at the breaker box.

Step 2. Rotate the multiport valve clockwise to the waste setting.

Step 3. Turn the pump on until the pool reaches your desired water level.

Step 4. Make sure to shut off your pump before turning the multiport valve clockwise to the filter or original setting.

Refilling your pool

Once you’re done draining, refill your pool with a garden hose. You can use two hoses to refill it and this will take around 14 to 16 hours.

What not to do when draining your pool

In general, DO NOT drain your pool water completely. If the problem can be solved by partially draining the pool, then that’s the best option. Drain a third or half of the pool water and then refill it quickly.

For some pool types, there are some things you need to keep in mind.

For vinyl pools, DO NOT drain it to the floor as the liner can shrink or wrinkle. If it’s needed to be drained completely (due to cleaning or repair), make sure to re-set or fix the liner while refilling. If it’s an in-ground vinyl pool, try not to drain it fully. This can damage the liner and pool surface.

For fiberglass pool, DO NOT drain it for long periods since it could pop or shift when drained completely. This can also damage the pool surface and liner. It’s best to drain it one-third at a time. Make sure to check the topography, elevation, and weather for rainfall.

For concrete pools, DO NOT leave it empty for a long period. This pool can be stable even when empty, but it’s better to fill it as soon as possible. When emptying concrete pools, make sure to open the hydrostatic valve and relief plugs in the main drain. 

When is the best time to drain a pool and how often should you do it?

Drain your pool when it’s warm or when the temperature is between 55 to 90°F. It’s not good for your pool surface to be exposed to cold temperatures. You also shouldn’t drain it when it’s too hot. If it’s more than 100 degrees outside, the plaster can get damaged and cracked, so you would have to replaster your pool.

Note: You can do partial draining at night if it’s too hot during the day. You should also time your draining so that it’s only empty when it’s about to be repaired. Don’t empty it a day, week, or month before the scheduled repair. 

Avoid draining a pool immediately after heavy rain because the water table adds extra pressure to the bottom. Do not drain your pool if it’s just regular pool cleaning since you can do it even with water. 

Drain your pool every five to seven years if it’s properly maintained or you haven’t encountered any pool issues. If it’s frequently used, you should do it every three to five years.

Kenneth Wilson
October 14, 2019
Yard & Garden

Kenneth Wilson

Retired contractor. Currently residing in Southwest Florida. Now in semi-retirement, I write and manage this blog focused on helping home owners make savvy decisions when it comes to finding contractors and getting their projects done. I also operate remodeling design service for homeowners.

Ask The Author Your Questions In The Comments!

{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}

More From This Author