---
title: "Pool Drain Calculator: CYA, Calcium, and TDS Issues"
description: Learn how to calculate the exact volume of water to drain and replace to lower high CYA, calcium hardness, or TDS levels in your Arizona swimming pool.
---

[blog](https://founderspoolservice.com/blog)

# [Pool Drain Calculator: CYA, Calcium, and TDS Issues](https://founderspoolservice.com/blog/pool-drain-calculator-cya-calcium-and-tds-issues)

 Written by [DC](https://founderspoolservice.com/blog/author/dc-1) | Jun 16, 2025 2:33:10 AM

**Why Draining Is Sometimes Necessary**

In Arizona’s hot and arid climate, pool water doesn’t get replaced as often as in other regions. That leads to gradual buildup of chemicals like **cyanuric acid (CYA)**, **calcium hardness**, and **total dissolved solids (TDS)**—each of which can cause long-term issues:

- High **CYA** reduces chlorine effectiveness.
- Elevated **calcium** leads to scale buildup and cloudy water.
- Excessive **TDS** can interfere with water balance and clarity.

When levels climb too high, chemical adjustments won't fix the issue. The solution? A **partial drain and refill**—but it’s important to calculate how much water to drain to hit your target levels.

 

**The Formula: Partial Drain Calculation**

To determine the correct percentage of water to drain and replace, use this simple formula:

**Drain Percentage (%) = (Current Level - Desired Level) / Current Level × 100**

This tells you what percentage of the pool needs to be replaced with fresh water to achieve your desired chemistry.

 

**Step-by-Step Example**

Let’s say you test your pool and find the following:

- **CYA (Cyanuric Acid): 180 ppm**
- **Desired CYA level: 60 ppm**

**Step 1:** Use the formula:

(180 - 60) / 180 × 100 = 66.7%

**Step 2:** Your pool is 15,000 gallons. Multiply:

15,000 × 0.667 = 10,005 gallons

➡️ **You should drain and replace approximately 10,000 gallons** to reduce CYA to 60 ppm.

 

**Same Approach Works for Calcium and TDS**

You can use this formula to reduce **calcium hardness** or **TDS** as well. Just plug in the current and target levels:

**Calcium Example:**

- Current CH: 800 ppm
- Desired CH: 400 ppm  
  → Drain 50% of your pool water.

**TDS Example:**

- Current TDS: 3,000 ppm
- Desired TDS: 1,500 ppm  
  → Drain 50% of your pool water.

 

**Important Tips**

- **Test after refilling.** Dilution may not be perfect—always retest levels after refill.
- **Use a sump pump safely.** Avoid draining below the skimmer unless you're using a submersible pump.
- **Never fully drain a pool** unless absolutely necessary and under professional guidance—especially plaster pools.
- **Schedule during cooler weather** to reduce surface stress during a drain.

 

**We Can Handle It For You**

Not sure how to safely drain and refill your pool? Founder's Pool Service offers **partial draining services** with expert water testing, high-efficiency pumping, and eco-friendly refills.

📍 Serving Buckeye, Verrado, Goodyear, Litchfield Park, North Scottsdale, Paradise Valley, and beyond.

 

**Call Today for Help With High CYA, Calcium, or TDS**

Let us handle your pool chemistry the right way—from testing to treatment. Call us or request a quote online.

[View full post](https://founderspoolservice.com/blog/pool-drain-calculator-cya-calcium-and-tds-issues)

```json
{
  "@context" : "http://schema.org",
  "@type" : "BlogPosting",
  "author" : {
    "@type" : "Person",
    "name" : "DC"
  },
  "dateModified" : "2025-08-17T23:42:42.927Z",
  "datePublished" : "2025-06-16T02:33:10Z",
  "headline" : "Pool Drain Calculator: CYA, Calcium, and TDS Issues",
  "image" : {
    "@type" : "ImageObject",
    "height" : 1536,
    "url" : "https://242600273.fs1.hubspotusercontent-na2.net/hubfs/242600273/Blog%20Drain%20Calc.png",
    "width" : 1024
  },
  "mainEntityOfPage" : "https://founderspoolservice.com/blog/pool-drain-calculator-cya-calcium-and-tds-issues",
  "publisher" : {
    "@type" : "Organization",
    "logo" : {
      "@type" : "ImageObject",
      "height" : 60.0,
      "url" : "https://242600273.fs1.hubspotusercontent-na2.net/hubfs/242600273/fulllogo_transparent_nobuffer-4.png",
      "width" : 143.01675
    },
    "name" : "blog"
  }
}
```