Pool Draining 101: How to Drain a Pool

There are plenty of reasons a pool owner may need to drain water, from starting the season with fresh water to completing repairs or resurfacing. More often, it comes down to water chemistry that has become difficult to manage, leading to recurring algae or cloudy water. Draining a pool takes planning, so it is important to know when it is truly necessary and how to do it safely!

When Should I Drain My Pool?

Luckily, you don’t have to drain as frequently as you might think! While the answer to this question isn’t a universal one, the general rule of thumb is to drain your pool every three to five years. Around that three-to-five-year mark, you might begin experiencing issues with your pool that can be hard to control.

You Find Yourself Struggling With Water Balance

Around the three-to-five-year mark, certain pool chemistry levels may rise above the recommended range. One of the biggest signs is ongoing trouble keeping water balanced, especially when Cyanuric Acid, Calcium Hardness, or Total Dissolved Solids climb too high. Stabilized chlorine products like trichlor tablets and dichlor shock can raise CYA over time. Hard fill water or frequent calcium hypochlorite shock can raise Calcium Hardness. TDS also builds gradually as the water is treated and used. When these levels get too high, adding more chemicals usually will not fix the root issue. In most cases, the solution is dilution or a full drain and refill.

As part of your overall pool maintenance routine, we recommend testing your pool water at least once a week as a way to keep track of your water balance over time.

You’re Noticing Changes in Your Pool’s Appearance 

Changes in appearance can be another clue. Persistent cloudiness or algae often points back to high CYA, high TDS, or high Calcium Hardness.

The harder your water, the harder it is to keep calcium scale from forming on pool surfaces — especially along the waterline and inside your pool equipment. Not only does this make the pool look bad, but it can actually lower the efficiency of your pool systems, including the pump, filter, heater, salt cell, and more. When Calcium Hardness approaches about 800 ppm or more, even prevention products may not be enough, and draining may be needed to regain control.

BONUS TIP: If your primary water source already has a high Calcium Hardness level, refilling with fresh water may not help much. In these cases, look into a water hauling service to deliver fresh, pre-treated water for your pool. This can often provide softer water than what’s available from the spigot.

Next up, Cyanuric Acid. Also known as stabilizer or conditioner, a high level can impact your chlorine efficiency. This can lead to issues with cloudy, unsanitary, algae-filled water as it loses its ability to break down organic contaminants. In addition, high Total Dissolved Solids leaves your pool oversaturated with minerals, salts, metals, and other materials.

You Need to Complete Pool Resurfacing, Repair, or Maintenance Projects

At some point, many pool owners will need to empty the pool to do certain types of repair work on interior pool surfaces. This can include acid washing to remove stains and scale. Repairs and maintenance may also involve resurfacing, repainting, or fixing cracks in the walls. If you have a vinyl liner in need of replacement, this, too, calls for a complete pool draining.

Important Tips Before You Start Draining Your Pool

• Before removing any water, check local rules for where pool water can be discharged, since many areas restrict draining into storm drains.
• Also consider groundwater. High groundwater can cause an empty inground pool to float or shift, especially after heavy rain, so it may be safer to consult a pro or only partially drain.
• Be careful with pool type. Do not fully drain fiberglass pools or inground vinyl liner pools, unless you are replacing the liner, because the surface or liner can bow, crack, or shift. For these pools, partial drain and refill in small increments is typically the safest approach.
• Protect your equipment by turning off the breaker before draining and removing timer trippers. Never use your pool pump to drain the pool, because it can lose prime and burn out. Always use a submersible pump to drain the pool.

How to Drain Your Pool

There are different ways to refresh your pool water, and it doesn’t always involve fully draining the pool. If you are experiencing minor issues with chemistry imbalances, pool owners can simply dilute the existing water. Start with draining a foot of water and then adding a foot of water at a time.

To remove water from the pool, you’ll need a submersible pump. Just as it sounds, a submersible pump is used completely underwater. Connect your submersible pump to a garden hose and then lower it into your pool. Once you turn the submersible pump on, the draining process will begin. If you’re only partially draining and refilling the pool, keep a close eye on the water level. Stop the submersible pump once the water lowers by a foot. Refill the water to normal operating levels, then retest the pool to see if you need to dilute the water further. Repeat as needed until your high CYA, TDS, or Calcium Hardness are back within ideal ranges.

If your pool is due for a full draining, we strongly recommend consulting a pool professional. Unfortunately, a lot of things can go wrong if a pool isn’t drained properly. In most cases, it’s best to have a licensed, bonded, and insured professional do the job for you.

BONUS TIP: Did you know that Leslie’s offers professional pool draining services? Stop by your local Leslie’s or fill out the appointment request form online to see if we provide services in your area. Our certified team of experts can also provide acid washing and tile cleaning services while the pool is empty.

Side Effects of an Improperly Drained Pool

Without sufficient research, preparation, and know-how, improperly draining your pool can lead to a number of issues, including structural and surface damage, flooding, damage to your home’s foundation, and more. This is why we highly suggest working with a licensed pool contractor who is familiar with local drainage laws and understands the best practices for safely draining a pool.

Even if you only plan to drain part of the water, be mindful of the time of year in which you drain your pool. Pool liners, fiberglass, and other sensitive pool surfaces are not designed to withstand sunlight without water. The same applies to plaster pools. Both intense heat and the sun’s rays can severely damage pool surfaces, leading to costly repairs. 

When possible, drain the pool when the outside air temperature is less than 85°F. Spring and fall are generally the best times to completely drain your pool. In the peak of summer, early morning and evening hours are the best times to dilute existing water or partially drain a pool.

Are You Ready to Drain Your Pool?

The best way to maintain a healthy pool and reduce the need for draining is to test your water weekly. Regular testing is the best indicator of the direction your water is heading. ​​For the most accurate water analysis, just bring a water sample to your local Leslie’s for a FREE in-store water test and a customized care plan. For more information on pool care and equipment maintenance, check out our blog, visit our YouTube channel, or stop by your local Leslie’s and speak with one of our experts!