Do I need to drain my pool or hot tub?

When you have a swimming pool, the last thing you want to think about is draining it. However, occasional draining is an essential part of keeping swimmers safe and your equipment running well. In this article, we'll explain why you need to drain your pool and how to handle the job.




Why draining is necessary

Even with regular maintenance, debris can build up in your pool. In the pool industry, we use the term Total Dissolved Solids (TDS) to cover the following contaminates that routinely get into the water:

  • Environment – minerals in rainwater, pollen, algae, dust, leaves, soil, vegetation, animal feces, and landscaping chemicals

  • People – sunscreen, lotions, oils, laundry detergent, hair, human feces

  • Cleaning Agents – chlorine, sodium bicarbonate, Cyanuric Acid (CyA), and other pool chemicals

Most of these contaminants are invisible to the naked eye, and since they are heavy and do not evaporate along with the water in your pool or hot tub, they build up over time. As the amount of TDS builds up, it can cause corrosion issues and eventually a hazy discoloration of your water.

Removing the old water and replacing it with fresh water is the best way to remove TDS and keep your water looking clear and fresh.

How often do I need to drain my pool or hot tub?

The answer depends on how many people use your pool and where it is located. Most backyard pools need to be drained or partially drained every three to five years. Whereas something like a backyard hot tub may need draining each year.

You can use a TDS meter, a small hand-held device, to measure the amount of TDS in the water. The best way to use a TDS meter is to get a base reading after you have filled your pool or hot tub with fresh water. Then, test the water every other week and note any increases.


The answer depends on how many people use your pool and where it is located. Most backyard pools need to be drained or partially drained every three to five years. Whereas something like a backyard hot tub may need draining each year.

You can use a TDS meter, a small hand-held device, to measure the amount of TDS in the water. The best way to use a TDS meter is to get a base reading after you have filled your pool or hot tub with fresh water. Then, test the water every other week and note any increases.


For a swimming pool, TDS levels vary widely depending on where you live, and what type of pool you have. While some pool companies have recommended TDS’s for draining, there is no hard and fast rule. If the pool starts having issues, and the TDS’s are high, then maybe its time. However, here in Utah, its not uncommon for a newly filled salt water pool to begin with over 3000 TDS, which is well beyond where many others might say it’s time to drain the pool.

For a hot tub, since there is less water in a hot tub than in a pool and people sweat more in a hot tub than a pool, the TDS will increase more rapidly in a hot tub than in a swimming pool. I’ve seen pools with TDS’s over 5000 parts per million(PPM) which have still been operating well within expected norms.

Another reason you might need to empty the water is if you need repair work on your pool or hot tub.


How do I drain my pool or hot tub?

Most municipalities have ordinances against discharging pool or spa water into storm drains. So, your first step is to check your local municipal code to find out when and where it is acceptable to drain the treated water. The usual process is to drain the water into one of your home's sewer cleanouts.


The best time to drain your pool is a dry period during the spring. You'll want to avoid having an empty or partially-empty pool exposed to temperatures above 85 degrees.

Delay the draining if there had been heavy rain recently. Rainfall that has increased the groundwater level in and around your pool causes an increased risk that the ground will push the pool to pop out as the water empties.

Depending on your hot tub's size, it should take around an hour to drain using the drainage spigot or about 10 minutes with a submersible pump. It should take back an hour to refill with a hose. The average time to drain a swimming pool is about 14 hours, and you can count on about the same time to refill it. You can save time if you can save more than one garden hose.


Important note: To prevent damage, you also should only partially drain a fiberglass or vinyl liner pool. Completely draining one of these in-ground pools could cause bowing or cracking.


We highly recommend that you do not drain your own fiberglass pool. Please give us a call. Usually, these pools need to be braced and checked even if there is no ground water. If you drain it on your own, your chances of damage are high.


Your next step is to turn off the power to your timers, pump, and pool light. Remove the drain plugs, open pressure relief valves, and leave all drains open.

Do not use your regular pool pump to empty your pool. It is designed to pull in water, so once your pool begins to drain, the pump will suck in air instead, potentially causing damage. We recommend that you rent or buy a submersible pump. Check that the electric cord can reach from your outlet to your pool. It's bs to avoid using an extension cord if possible.

Place the submersible pump on the floor in the center of the deep end of your pool. Be careful to place the drainage hose where you want the water to drain. Sometimes, the water pressure will move the hose slightly, so it's a good idea to double-check it after the water begins to drain.

Then keep checking on cords and the hose to make sure that the process is going smoothly. Although it might sound tempting to do the draining at night, you'll want to keep an eye on the process to make sure a flood doesn't occur. With a swimming pool, you are draining thousands of gallons of water!

Monitor the water level according to the type of pool you have and how much water you want to remove. Even if you are fully draining, it's not necessary to empty every inch of water. Eventually, the water level will be so low that the submersible pump will no longer be able to work. When this happens, turn the pump off and remove it from the pool. Open the relief valves if your pool's valves are not automatic.


A drained pool is a vulnerable pool, so as soon as you have done the repairs, cleaning, or maintenance that needs to be done, it's time to refill the pool or hot tub with clean water. First, close the relief valves and drains.


As soon as possible after you have refilled the pool, test the water with your TDS meter to get that base reading.

If all this work sounds mentally draining, give the experts at Tops Pools a call. We'll talk you through the process or help you get the professional help you need.