How to Safely Drain an Inground Pool with A Sump Pump

Knowing how to safely drain an inground pool could save your marriage. Just try telling the spouse that the pool popped out of the ground and the repairs are going to cost as much as a new pool.

You probably have an inground pool to enjoy a clean, refreshing swim whenever you want.  So, it’s probably never a good idea to drain your pool as this would convert it into a skate park! It is also true that once you have drained your pool you will at some stage have to refill it again, and that will cost you a lot of money.

All Inground Pools Must Be Drain Eventually

The reality is that if you have had your pool for long enough, there will be a time that you will have to drain it. It is a good thing that this is not a weekly, monthly, or even yearly process.

You do however have to realize that it’s likely you’ll have to drain your pool once every few years. When that happens, it’s crucial that the job is done perfectly. If you drain your inground pool without following the proper process, it could get seriously damaged.

In this article, we’ll explain when you should drain your pool, how to safely drain an inground pool, and what you should do to refill it.

Why Does a Swimming Pool Need to be Drained?

There are very few scenarios that will require you to completely drain your pool and that is why it only has to be done once every few years. If none of the reasons described below apply, there should not really be any reason why you would want to drain your pool.

Maintaining Your Pool

Most often, the maintenance that routinely needs to be done on a pool can be performed without having to drain the water. A high-performance automatic pool cleaner should for example be able to withstand coming into contact with water.

However, if your pool freezes during the winter months, some of the water must be removed from the pool beforehand.

Man inspecting a drained inground pool.

Also, there are scenarios where one-off maintenance can only be done on an empty pool. This would include things such as repainting the bottom of the pool, repairing a cracked pool floor, and cleaning extreme calcium deposits and metal stains.

Reset The Chemical Balance Within the Water

It can happen that the chemical balance of pool water over time gets so out of hand that it’s best to simply let it go and start afresh. This makes sense and it eventually happens to all pools.

The same pool water has likely been in your pool for many years and to keep it hygienic and clean, we constantly have to add sanitizers such as chlorine and other chemicals.

However, there is one element that needs to be considered in this situation and that is what happens to the remnants of those chemicals, together with debris, dirt, and other contaminants.

These are known as the total dissolved solids (TDS) in your pool water, which will build up over a long period of time. This can have serious negative consequences for the water chemistry.

The pool water’s TDS can be monitored with test strips or a digital meter. Once it exceeds around 1,500 ppm (parts per million), the time has come to drain your pool and start fresh.

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When You Should Drain Your Pool – 5-Step Checklist

The first rule of pool draining is that you need to do it as quickly as possible. The last thing you want is to sit with an empty pool for an extended period. My suggestion is that you make sure it’s not empty for longer than a week.

If you follow the checklist below it will help ensure that you’ll be able to cope when you start draining your pool.

Follow These Steps On How to Safely Drain an Inground Pool

1. When You Have Enough Time Available

You don’t want to have your pool sitting empty for more than a week. However, you will also need a significant amount of time while it’s draining, as it’s not a good idea to move thousands of gallons of water unattended.

It generally takes 8 hours or more to drain a pool completely, and it can even take as long as 16 hours. Filling your pool will take just as long.

2. When You Can Afford It

Emptying and refilling a pool is not cheap – you are after all draining and replacing up to 20,000 gallons of water. It would be a really good idea to budget ahead for that month’s water bill.

Two little girls having fun in the pool on a sunny day.

3. On a Sunny Day, But Not When It’s Too Hot!

Although you don’t want to drain your pool in the pouring rain, you can also not do it on any sunny day. If the sun is too hot, it can cause serious damage to your pool.

If you drain it during a heat wave, there will likely be damage ranging from the pool liner, to even pool floors and walls being cracked.

An empty pool should never be exposed to heat higher than about 85°F (29°C).

4. Prep Your Circulation System

You should always turn off the power to all pool systems before draining your pool.

If your automatic timer is left on, the pump can come on at any stage while you’re draining the pool. This will result in air being pulled instead of water and will lead to the pump overheating. In extreme cases, the pump will even melt.

Pool lights coming on while the pool is empty will heat up and shatter because the pool water normally keeps the lights cool.

5. Ensure The Pool’s Chemical Levels Are Down

Your local water authority will likely require that any pool water that is drained does not contain high pool chemical concentrations. For the exact requirements, speak to your local water authority.

Before I drain the pool, I stop treating the water far ahead of the time. I use test strips to ensure that the water has a neutral pH, is chlorine neutral, and doesn’t contain high levels of other chemicals.

Wait Until After Spring Rains to Prevent Inground Pool Popping!

Although it is tempting to skip ahead to the part about how to safely drain an inground pool, these precautions are here because there is a lot that could go wrong.

The worst danger is what is known as a pool pop. In this scenario, the pool acts like a boat. When the ground water level rises, it pushes the pool “boat” upwards out of the ground.  Usually, the bottom of the pool is pushed out of place which cracks the plastic pipes underneath it. Additionally, the pool shell itself will also likely crack.

In this case, the top edge of the pool will also come loose or crack. Also, the concrete decks surrounding the pool will be damaged.

If that wasn’t bad enough, the pool lights’ electric wiring will be damaged, which may even lead to electrocution.

Sadly, homeowners’ insurance will rarely cover this type of damage. The safest way to make sure that a pool does not pop when being emptied is to hire professionals to drain the pool. If something does happen, then the pool contractor’s insurance should pay for the damages.

This is especially true if you have a high risk of this happening, i.e. if it has rained recently, or if there is a high water table in your area.

A high water table is created when the earth is saturated with water. This can happen anywhere. Particularly after a heavy rain.

The water soaks into the ground and combines with an already existing water source. Such as an underground stream, a spring or lake. These natural water sources cannot hold additional water and so the water rises towards the surface.

A man standing in the rain.

I worked within a complex of buildings that were connected by underground tunnels. Every spring the heavy rains would soak into the ground and combine with an underground river that flowed nearby or under the tunnels. The extra rain water forced water through the concrete tunnel floors. When the spring rains stopped so did the flooding of the tunnels.

The tips described below should help you avoid this specific problem.

Plan Where the Water Will Go

As you are going to move thousands of gallons of water, you need to have a plan before you start to drain the pool.

Simply pumping it into your yard is not an option. That water is going to act like a lake under the pool and try to push your “inground boat” pool upwards out of the ground. So, if you pump the water into the ground close to your pool, you’ll probably regret it.

Also, you don’t want water that has been treated with chemicals going into your garden and potentially killing off your grass and plants.

To determine where you may pump all that water, consult with your local water authority. The normal process is to pump the water into the household sewer drain. Which means the sewer plant must treat that additional water.

However, that is sometimes preferable to dumping the water into a street storm water drain. Which could harm the water quality of local streams and rivers.

Many cities and counties restrict where a pool can be drained. Go to your local government website to find the regulations that apply to you.

To prevent the pool from popping up, ensure the drainage hose will reach the point where the local authority will allow you to drain your water.

Also, make sure the drainage hose runs downhill from the pool in case other drainage problems happen.

One way to find out if the sewer pipe is partially clogged is to pump thousands of gallons of water into it. Many household’s drain pipes are partially plugged with fats and grease. Which usually allows normal amounts of water to pass through. However, that partial clog acts like a dam and all that water could back up into the house or yard.

If something does go wrong and the water comes back toward you, you want to make ensure it’s far away from your pool.

Don’t Drain Your Pool Shortly After It Rains

The worst time to drain a pool is during stormy weather. If rain has recently sunk into the yard, this will have created more water pressure around and under the pool. This will increase the risk of the pool popping out of the ground as the water empties.

Allow the ground to dry out for a few weeks before starting to drain your pool. Although the surface of the ground may look dry, that doesn’t mean the earth below the ground surface is dry. You don’t want to find out the hard way by your pool popping up.

Understand Your Pool’s Relief Valves

The hydrostatic pressure relief valves in a pool are a safety feature that has been designed to prevent a pop up. If you have never drained your pool before, you might not even be aware that they exist.

Take a look at the bottom of the pool. See those white rings that have been plastered into the pool’s floor? These are screwed into a pipe underneath. That pipe runs under the pool’s floor to an underground gravel pit under the pool.

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These valves will allow water that has accumulated underground to push up into the pool when it is emptied. Without the valves, the underground water may create enough pressure to pop the pool.

You should remove these rings once the pool is nearly completely drained to relieve the pressure. Be sure to have a few extras available in case they are damaged when you remove them.

The 5 Steps of the Draining Process

As you now know how to drain an inground pool safely, it’s time to start the actual draining process.

1. Use a Submersible Pump to Drain the Pool

You can’t use a regular pool pump to drain your pool as it was designed to suck in water, and once your pool has started draining, it will suck in air. This could lead to it being damaged permanently.

You should buy or rent a submersible pump to empty the pool. This is not too expensive.

Make sure the submersible pump’s power cord can reach from the floor of the pool to the outlet and place the pump on the floor in the middle of the deep end. If possible, don’t use an extension cord – it’s safer not to.

Connect a hose to the submersible pump and the other end should be placed wherever the water will be pumped to.

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2. Start Draining the Pool

Start draining by turning the submersible pump on. Usually that just means placing the pump in the water and then plugging it into an electrical outlet. Be sure that it is a GFCI protected electrical outlet. That will protect you and the pump from being fried.

You need to keep an eye on this, no matter how long it’s going to take. Monitor the hose and the cords to ensure that all keeps going smoothly and no accidents happen.

One thing you may want to consider when you drain your pool is to switch the pool over to saltwater. This will help your chlorine operate at the most consistent, safest, and lowest levels possible.

3. Remove the Submersible Pump

The water will drop to a level that is too low for the submersible pump to push any of it out of the pool. This is normal and it’s seldom that every inch of water can be drained.

Although, you could switch to a pool cover pump which typically pumps water down to a lower level. However, pool cover pumps generally have lower flow rates and that will take longer to drain the pool.

The water that’s left won’t affect your pool’s chemical balance in the future. Turn off and remove the submersible pump.

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4.  Open the Pressure Relief Valves

Open the hydrostatic pressure relief valves to ease the pressure of the underground water as this will prevent the pool from popping up.

5. Do the Work That Required the Pool Draining

If the reason for draining the pool was to fix the chemical balance, immediately start refilling it using the 3 steps below.

However, If there is work to be done, like painting or repairing the pool, that can be done now.

If the floor needs to be totally dry to work on, you can use a durable, heavy-duty cover pump such as the Sunnora 1500 GPH Pool Cover Pump.

Proceed to the next steps to refill your pool as soon as possible. Remember, you don’t want to leave the pool empty for longer than a week.

The 3 Steps to Refill an Inground Pool

Although refilling a pool is a lot easier than draining it, it will take some time and you will have to rebalance your water.

1. Replace the Pressure Relief Valves

Close the pressure relief valves. They should not be open when you fill up your pool with water as the water will then fill the gravel pit and create massive pressure. Put Teflon tape on the plug’s threads and twist it tightly into the valve.

2. Refill the Pool and Switch on the Pool’s Circulation Pump

Boy sitting in a pool float after the pool had been refilled.

Use as many garden hoses as you have to refill the pool.

Does the water source contain manganese, iron, chromium or copper metals? Then it’s a good idea to use hose filters to remove those metals. If you don’t do this, you will have to fix ugly metal stains later.

Which may even result in you having to drain the pool again. That’s definitely something you want to prevent from happening if you can.

3. Balance the Water Chemistry

You need to balance the water chemistry from scratch, just like you would do when your pool is opened for the season for the first time. This is the trickiest part of refilling a pool.

It’s Pool Enjoyment Time!

Well, not quite yet. Be sure you have a working pool heater because that fresh water is probably going to be too cool for comfort. However, now you are ready to enjoy a summer of fun and relaxation in the pool. Enjoy!

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