Why and How to Partially Drain Your Pool: A Comprehensive Guide
Keeping your pool in top condition often requires a bit more than just regular cleaning and chemical balancing. One crucial maintenance task that homeowners sometimes overlook is partially draining the pool. If you’ve noticed that you’re doing this more often than in the past, there are several good reasons why this might be necessary.
Reason You Might Need to Partially Drain Your Pool
1. High Total Dissolved Solids (TDS): Over time, particles in pool water accumulate, increasing the TDS levels. When TDS rises above 1500 ppm over the base water level, it can cause cloudy water and hinder the effectiveness of your pool chemicals. Draining a portion of the water can help reduce TDS levels and improve water clarity.
2. High Cyanuric Acid (CYA): CYA is beneficial in moderating chlorine activity, but excessive levels can lead to ineffective chlorine and cloudy water. If your CYA levels are too high, draining a portion of the water and refilling it can help bring them back to a manageable level.
3. High Phosphates: Phosphates can promote algae growth and contribute to cloudy water. If phosphate levels are above 4000 ppb, along with other issues like high TDS, it might be beneficial to partially drain the pool before treating the phosphates to get better results.
4. Inability to Maintain Chlorine Levels: If you’re struggling to keep chlorine levels stable, high nitrate levels might be the culprit. A partial drain can help reduce the amount of chlorine needed to overcome severe nitrate issues and make managing chlorine levels easier.
Why You Should Avoid Fully Draining Your Pool
1. Vinyl Liner Concerns: For pools with vinyl liners, fully draining the pool can cause the liner to float and potentially never return to its original position. This can lead to significant issues with the liner’s fit and functionality.
2. Water Table Issues: If the water table around your pool is high, fully draining the pool can lead to the pool “popping” out of the ground due to the hydrostatic pressure.
3. Structural Integrity: Draining the pool completely can compromise its structural integrity. It’s generally safer to drain only a portion of the water.
(This is an example of what can happen if the water table is too high and your pool doesn't have enough weight to keep it in the water)
What to Do Before Draining Your Pool
1. Check Local Codes: Ensure you understand and follow local regulations regarding pool water drainage. In many areas, draining directly into storm drains is not permitted.
2. Open the Auto Cover: Fully open your auto cover and keep it open until the pool is refilled to the middle of the skimmer openings to prevent potential damage.
3. Consult on Flocculants or First Aid: Depending on your pool’s condition, using a flocculant or a first aid treatment before draining might be advisable. These products can help remove unwanted particles more effectively.
How to Drain Your Pool
Option 1 - Submersible Pump: We have found the safest way to prevent over-drainage is to put an auto cover pump onto the second step of the pool so it does not drain below that level, and to run a hose into your pool skimmer at the same time to refill as you empty.
- Turn off the skimmers in case the water level gets too low, and turn them back on after refilling.
- Place an auto cover pump on the second step of the pool.
- Use a hose to refill the pool while the pump is draining. Adjust the pump’s height to prevent it from draining too much water
Option 2 - Main Drain: Alternatively, you can drain via the main drain if you have a waste line on the pool (generally pools with Sand and DE Filters, but sometimes a Cartridge filter will have one). CYA is denser than water, so this method can be more effective for removing high CYA levels.
You will need to watch the water level carefully to make sure it doesn't go below the return lines, leaving at least a foot in the shallow end of the pool.
- Roll out the backwash hose to an approved drainage area.
- Turn off the pump and close the skimmer valves.
- Leave the main drain valve open.
- Set the multiport valve to the “Waste” position or open the waste valve.
- Turn the pump on and drain the desired amount of water. For extra security and to get more water replaced at the same time, add a hose to the top of the pool to refill as it drains out the lower water.
- Once done, rotate the multiport valve back to “Filter” and turn the pump on again.
- Pick up the backwash hose and roll it up.
Option 3 - Vacuum to Waste: If you are utilizing a flocculant before draining, to pull out the worst contaminants in the water, you can also vacuum to waste, assuming you have a waste line (generally pools with Sand and DE Filters, but sometimes a Cartridge filter will have one). This is generally safer than draining through the main drain since you are forced to stay by the pool and monitor the water level, and can be more beneficial since you have dropped the worst offenders to the bottom and can vacuum those directly out.
To vacuum to waste, see our instructions on vacuuming to waste.
Refilling the Pool
1. Use a Hose Filter: If your fill water has high metal content, we highly recommend attaching a hose filter like the Pleatco Pre-Filter to purify the water as it enters the pool. Fill the pool at half-speed to minimize impurities.
2. Start Refilling Early: You can start refilling the pool even as you are draining water to turn over the water more quickly. Just make sure it is in a different location to ensure you are draining older pool water and the new water remains.
Regular maintenance and understanding how and when to partially drain your pool can make a big difference in keeping your water clean and your pool in top shape. If you’re unsure about any part of the process, it’s always a good idea to consult with a professional to ensure the best results for your specific pool.
