When and How to Drain Your Pool: A DFW Homeowner's Guide

Draining a pool is one of those jobs that sounds simple but carries real risks if done wrong. A drained pool can pop out of the ground, crack its shell, or suffer permanent surface damage — and in DFW, the expansive clay soils make these risks higher than in most areas. Yet sometimes draining is the only solution to a water chemistry problem or a necessary step before a repair.

Here's when you actually need to drain, when you don't, how to do it safely, what it costs in the DFW area, and how to properly treat the refill water.

When Draining Your Pool Is Necessary

Most pool problems can be solved without draining. But there are specific situations where a partial or full drain is the only option.

Reason 1: Cyanuric acid (CYA) is too high

CYA (stabilizer) does not break down, evaporate, or get consumed. The only way to lower it is to dilute it by replacing water. If your CYA has climbed above 80-100 ppm, chlorine becomes increasingly ineffective regardless of how much you add.

What to do: A partial drain and refill is usually sufficient. Draining 50% of the water and refilling cuts CYA roughly in half.

For the full details on this issue, see: High CYA Levels and How to Fix Them

Reason 2: Total dissolved solids (TDS) are too high

TDS is the sum of everything dissolved in your water — minerals, salts, chemical byproducts. Over years, TDS accumulates as water evaporates and concentrates these solids. High TDS (over 2,500 ppm for traditional chlorine pools, or over 6,000 ppm for saltwater pools) can cause:

• Cloudy water that won't clear
• Poor chlorine performance
• Scale formation
• Salty or metallic taste
• Staining

What to do: A partial or full drain and refill is the only fix.

Reason 3: Pool resurfacing or structural repair

Most resurfacing jobs (replaster, pebble finish, tile replacement) require a full drain. You can't replaster a pool with water in it.

Structural repairs — fixing cracks, patching, repairing plumbing penetrations — also typically require draining.

See: Pool Plaster Resurfacing Cost Guide

Reason 4: Severe contamination

If something has contaminated the pool beyond what chemical treatment can fix — such as a sewage backup, certain chemical spills, or extremely heavy metal contamination — draining and starting fresh may be the safest option.

Reason 5: Copper or metal staining that won't respond to treatment

High copper (from copper algaecides, copper pipes, or well water) or other dissolved metals can stain pool surfaces. If ascorbic acid treatment and sequestrants can't resolve it, a drain may be necessary to remove the metal-laden water.

When You Should NOT Drain Your Pool

Draining is an aggressive action. Don't do it unless you genuinely need to.

Don't drain for algae

Even a severely green pool can be recovered with proper chemical treatment. Shocking, brushing, filtering, and vacuuming is cheaper, faster, and far less risky than draining. Draining a pool with algae can leave stains on the exposed surface that are difficult to remove.

Don't drain for cloudy water

Cloudy water has a chemical cause that can almost always be solved without draining. Proper filtration, chemical adjustment, and clarifiers will fix it. See: Cloudy Pool Water: Causes and Fixes

Don't drain for routine chemical adjustment

pH, alkalinity, calcium, and chlorine can all be adjusted without draining. The only chemicals that cannot be removed by normal means are CYA and TDS (which is everything combined).

Don't drain after a freeze

Frozen pool water can damage tile and coping, but the water in the pool actually protects the shell from ground pressure. Draining a pool after a freeze removes that protection and increases the risk of structural damage.

Don't drain if the water table is high

After heavy rains (and DFW gets some intense spring storms), the water table rises. Draining a pool when the surrounding soil is saturated with water removes the counterweight that keeps the pool in the ground. This is how pools "pop" — literally lift out of the ground due to hydrostatic pressure.

The Risks of Draining a Pool

Understanding the risks helps you make the right decision and take proper precautions.

Hydrostatic pressure (pool pop)

Your pool shell sits in the ground like a boat in water. The weight of the pool water pushes down, counteracting the upward pressure of groundwater. Remove the water, and groundwater pressure can lift the pool shell out of the ground.

DFW-specific risk: North Texas has expansive clay soil (primarily Eagle Ford and Austin Chalk formations). These soils absorb water and expand significantly. After rain events, the water table can rise quickly. Clay soils also exert lateral pressure on pool walls.

Mitigation:

• Check for hydrostatic relief plugs at the bottom of the main drain. These plugs allow groundwater to enter the pool (rather than push up the shell) when the pool is empty.
• Never drain during or immediately after heavy rain.
• Drain and refill as quickly as possible — don't leave the pool empty for days.
• Monitor weather forecasts before draining.

Shell damage from sun and heat exposure

An empty plaster pool in DFW summer heat faces surface temperatures exceeding 150 degrees F. This can:

• Cause plaster to dry out, crack, and delaminate
• Shrink and crack vinyl liners permanently
• Damage tile adhesive, causing tiles to pop off
• Bleach and discolor the surface unevenly

Mitigation:

• Drain in cooler months (fall or early spring) when possible.
• If draining in summer, work quickly and keep the surface wet.
• Never leave a pool empty in full sun for more than 2-3 days without wetting the surface.

Structural stress

The water in your pool provides structural support to the walls, especially for fiberglass and vinyl pools. Removing this support can cause:

• Fiberglass pools to buckle or crack
• Vinyl liner pools to shrink and pull away from the walls
• Concrete/gunite walls to develop cracks from soil pressure

Equipment damage

If the pump runs without water, it will overheat and destroy the seal, impeller, and potentially the motor within minutes. Make sure all equipment is off before the water level drops below the skimmers.

Partial Drain vs. Full Drain

In most situations, a partial drain is the safer and better option.

Partial drain (recommended for most situations)

What it is: Draining 25-75% of the pool water and refilling.

Best for:

• Lowering CYA
• Reducing TDS
• Diluting metals or other dissolved contaminants
• After heavy stabilized-chlorine use

Advantages:

• Maintains weight in the pool to resist hydrostatic pressure
• Surface never fully dries out
• Faster process
• Lower water cost
• Less risk of structural damage

The math: Draining 50% and refilling cuts the concentration of dissolved substances approximately in half. If your CYA is 120 ppm and you drain and refill 50%, you'll end up around 60 ppm. To get from 120 to 40, you'd need to drain about 67%.

Starting CYA	Drain 25%	Drain 50%	Drain 67%	Drain 75%
80 ppm	60 ppm	40 ppm	26 ppm	20 ppm
100 ppm	75 ppm	50 ppm	33 ppm	25 ppm
120 ppm	90 ppm	60 ppm	40 ppm	30 ppm
150 ppm	112 ppm	75 ppm	50 ppm	37 ppm
200 ppm	150 ppm	100 ppm	66 ppm	50 ppm

Full drain

What it is: Removing all water from the pool.

Required for:

• Resurfacing (replaster, pebble, tile)
• Structural repairs
• Major plumbing repairs at the pool shell
• Severely contaminated water that cannot be partially diluted

Risks: All the risks listed above — hydrostatic pop, surface damage, structural stress. Only drain fully when there's no alternative, and work quickly to refill.

How to Drain Your Pool: Step-by-Step

What you'll need

• Submersible pump (sump pump) — rent one if you don't have one, typically 1/2 to 1 HP
• Discharge hose long enough to reach the drain point
• Garden hose for refilling
• Test kit for refill water treatment
• Time — a full drain takes 8-18 hours depending on pool size and pump capacity

Step 1: Check the weather and water table

• No rain in the forecast for the next 3-5 days
• No rain in the previous 3-5 days (soil needs to be relatively dry)
• Ideal DFW months: October, November, March, April (moderate temperatures, drier periods)
• Avoid: May-June (heavy storm season), July-August (extreme heat)

Step 2: Know where to drain the water

This is important and regulated. In the DFW area:

Where you CAN drain pool water:

• Into the sanitary sewer cleanout on your property (preferred method)
• Into the street gutter/storm drain only if your city permits it and the water is dechlorinated

Where you CANNOT drain pool water:

• Into creeks, streams, or natural waterways
• Onto neighboring properties
• Into areas that will cause erosion or flooding

City-specific regulations:

• Most DFW cities (including those in the Northlake area) prefer or require draining to the sanitary sewer via a cleanout
• Some cities require notification before draining large volumes
• Check with your specific city's water/sewer department before draining
• Dechlorinate before draining — let chlorine drop below 0.1 ppm, or add a dechlorinator

Step 3: Prepare the pool and equipment

1. Turn off all pool equipment — pump, heater, salt cell, automation, chlorinator
2. Remove the drain plugs from the equipment if draining below the equipment level
3. Open the hydrostatic relief plugs at the main drain if doing a full drain (some pools have them, some don't)
4. Remove any items from the pool — toys, floats, cleaners, ladders
5. Note the location of your pool light — if the water drops below it, the light niche will be exposed

Step 4: Set up the drain pump

1. Place the submersible pump in the deepest part of the pool
2. Connect the discharge hose
3. Run the hose to the sanitary sewer cleanout (or approved drain point)
4. Secure the hose so it won't pop out under pressure
5. Turn on the pump and verify water is flowing to the correct location

Step 5: Monitor the drain

• Do not leave the drain unattended for long periods. Check every 1-2 hours.
• Watch for signs of ground movement or shell stress
• If you hear cracking or see the shell shift, stop draining and begin refilling immediately
• Note when the water drops below the skimmer — your pool pump should already be off at this point

Step 6: For partial drains — begin refilling

Once you've drained the target percentage:

1. Turn off the submersible pump
2. Begin refilling with the garden hose (or call a water delivery service for faster fill)
3. Place the hose in the deep end to avoid surface splash damage
4. Monitor the fill level

Step 7: For full drains — work quickly

If the pool is fully drained for repairs or resurfacing:

• Complete the work as quickly as possible
• Keep the exposed surface wet (spray with a hose periodically) if the work allows it
• Begin refilling as soon as the work is complete
• Don't leave the pool empty overnight if rain is in the forecast

Refill Water Cost in the DFW Area

Water costs vary by city and provider in the DFW area. Here are approximate costs for refilling based on 2025-2026 municipal water rates:

Estimated refill costs (municipal water)

Pool Volume	Water Used	Approximate Cost
10,000 gallons	10,000 gal	$40-$70
15,000 gallons	15,000 gal	$60-$100
20,000 gallons	20,000 gal	$80-$140
30,000 gallons	30,000 gal	$120-$200
40,000 gallons	40,000 gal	$160-$280

Note: Most DFW municipalities use tiered water pricing. Pool refills push you into higher tiers, increasing the per-gallon cost. Your actual cost depends on your total household water usage for that billing cycle.

Alternative: Water delivery by truck

For faster fills, you can hire a water delivery company to fill your pool by tanker truck.

• Cost: $200-$600 for a full pool (typically $300-$500 for an average DFW pool)
• Speed: A tanker can deliver 6,000-8,000 gallons per load, filling most pools in 2-4 loads over a few hours
• Advantage: Much faster than a garden hose (which takes 24-72+ hours for a full fill)
• Consideration: Tanker water may come from wells and have different chemistry than municipal water — test after filling

Filling with a garden hose: timeline

Pool Volume	Approximate Fill Time (standard garden hose, ~8 GPM)
10,000 gallons	~21 hours
15,000 gallons	~31 hours
20,000 gallons	~42 hours
30,000 gallons	~63 hours

A standard garden hose delivers roughly 7-10 gallons per minute. Two hoses cut the time roughly in half.

Refill Water Treatment: Getting the Chemistry Right

Fresh tap water is not ready for swimming. It needs treatment before the pool is safe and the chemistry is balanced.

Refill water treatment protocol

Follow this order after filling:

Step 1: Test the fill water Test pH, alkalinity, calcium hardness, and CYA. DFW tap water typically has:

• pH: 7.8-8.5 (high)
• Alkalinity: 140-220 ppm (high)
• Calcium hardness: 200-300 ppm (usually okay)
• CYA: 0 ppm (none)
• Chlorine: 1-3 ppm (city chloramine — not pool-grade)

Step 2: Lower alkalinity and pH (if needed) DFW water almost always comes in with alkalinity and pH above target. Add muriatic acid to bring alkalinity to 80-120 ppm and pH to 7.2-7.6. Do alkalinity first, then fine-tune pH. See: How to Lower Pool Alkalinity

Step 3: Add CYA (stabilizer) Fresh fill water has zero CYA. Your chlorine will be destroyed by UV within hours without protection. Add CYA to reach 30-50 ppm. Use granular cyanuric acid in a sock or dissolve in warm water.

Step 4: Add chlorine Once CYA is dissolving (start after adding, don't wait for full dissolution), add liquid chlorine to reach 3-4 ppm. Continue daily chlorine additions as the pool stabilizes.

Step 5: Adjust calcium hardness (if needed) If your fill water is below 200 ppm calcium (uncommon in DFW but possible with some water sources), add calcium chloride.

Step 6: Consider a metal sequestrant DFW tap water and especially well water can contain iron, copper, and manganese. A metal sequestrant binds these metals and prevents staining during the critical first few weeks. This is especially important if your water has any color or metallic taste.

Step 7: Run the pump continuously for 24-48 hours Full circulation helps distribute chemicals evenly and clear any initial turbidity.

Refill startup chemical checklist

For a typical 15,000-gallon DFW pool:

Chemical	Approximate Amount	Purpose
Muriatic acid	1-2 gallons	Lower pH and alkalinity
Cyanuric acid (CYA)	3-5 lbs	UV protection for chlorine
Liquid chlorine (12.5%)	1-2 gallons	Sanitize
Metal sequestrant	Per label (typically 32 oz)	Prevent metal staining
Calcium chloride	Only if needed	Raise calcium hardness

When to Hire a Professional

Some drains are better left to the pros:

• Full drains on older pools — Pools over 15-20 years old may have hidden structural issues that a professional can assess before draining.
• Fiberglass pools — These are particularly susceptible to bulging and cracking when empty. Professional monitoring is strongly recommended.
• Pools with known groundwater issues — If your yard stays wet or you have a high water table, a professional can manage the hydrostatic relief system.
• Pools needing resurfacing — The drain is just the first step. The resurfacing contractor will handle the drain as part of the project.
• If you're unsure about anything — The cost of a professional drain ($200-$500) is a fraction of the cost of repairing a popped or cracked pool shell ($10,000-$50,000+).

Partial Drain Alternative: Dilution Over Time

If your CYA is moderately high (70-100 ppm) and you want to avoid draining, there's a slower alternative:

1. Backwash your filter more frequently — each backwash removes 200-500 gallons of old water
2. Allow rain to overflow the pool — this dilutes CYA naturally (don't drain rain off the pool)
3. Use liquid chlorine instead of tablets — stop adding more CYA while the natural dilution works
4. Top off with fresh water — as water evaporates and gets replaced, CYA gradually drops

This approach takes months but avoids the risks of draining. It works best for pools that are only moderately high on CYA.

Ready to Drain? We Can Help.

If your pool needs a drain and refill, Simplified Pools offers professional drain services throughout the Northlake and DFW North area. We handle the drain, monitor for structural risks, and get your water chemistry dialed in perfectly on the refill.

• Get all the startup chemicals you need: Simplified Pools Supply Store
• Shop online for chemicals and supplies: Simplified Pools Online Shop
• Schedule a drain service or get advice: Contact Us
• Call us directly: (469) 455-1054
• See all our services: Pool Services

We'll test your water first to confirm draining is actually necessary. Sometimes there's a better, cheaper solution — and we'll always tell you if that's the case.