How to Safely Drain a Fiberglass Pool if Necessary
Most fiberglass pools never need to be drained, and emptying one the wrong way can damage it. This guide explains why, when draining is justified and who should handle it.
Short answer: Not on your own. An empty fiberglass pool can be lifted or cracked by groundwater, and the walls can bulge without the weight of the water. Latham says to consult your dealer before draining. If draining is truly necessary, a qualified professional should plan it using the pool maker’s written instructions.
Can you drain a fiberglass pool?
Physically, yes. In practice, draining is a decision for the pool maker’s instructions and a qualified professional, not a weekend task. Latham’s own guidance says you should never drain a fiberglass pool without first consulting your dealer.
Latham’s current warranty also states that the pool is designed to remain full of water at all times. It excludes damage that results from “improper or unauthorized draining” or from the groundwater table rising above the pool water level. Other manufacturers have their own wording, so check the written instructions that came with your pool.
Why can draining damage a fiberglass pool?
Two forces work on the shell once the water is gone.
- Groundwater pushes up. Latham explains that when too much water is in the ground around the pool, the pressure can force water upward and crack or float the bottom of the pool.
- The walls lose support. Latham notes that the weight of the water helps hold the fiberglass walls in place. Without it, the walls can bulge and the floor can split. That can mean repairs to the plumbing and deck as well as the shell.
Latham says the risk of damage is even greater for fiberglass than for other pool types.
What is a hydrostatic relief system?
Latham says a sump line or a daylight drain is installed at the deep end of the pool during installation to help balance hydrostatic pressure. Which setup your pool has depends on how it was built. Your installer can tell you what yours has, and your pool maker’s written instructions should say how it figures into any draining plan.
When is draining actually necessary?
Rarely. Latham says only in the rarest cases would a fiberglass pool need to be drained for cleaning. Cloudy water, algae and stains are normally handled with chemistry, filtration and brushing. Our care and maintenance guide and our guide to water balance cover the routine side.
Draining is not part of closing the pool for winter either, since the pool is designed to stay full. Our winter safety covers page covers the off-season side.
Structural repair is the case Latham’s warranty anticipates. The warranty’s repair language refers to bracing the pool and removing groundwater from around it. That is a good indication of how much more is involved than pumping water out. If a pool needs work like this, see our guide to fiberglass pool durability and repair.
What should be checked before the pool is drained?
A professional should assess the ground around the pool before any water leaves. The main question is whether groundwater is high enough to push on an empty shell. Latham’s warranty ties damage to groundwater rising above the pool water level and to runoff collecting around the pool and deck.
Before you call, note anything that could bear on that assessment:
- Recent heavy rain or standing water near the pool.
- Any past issues with water collecting around the deck.
- The name of the installer or dealer who set the pool, and your warranty paperwork.
Do not start draining to find out what happens. Latham warns that the resulting damage can be extensive.
Who should drain a fiberglass pool?
Start with the dealer or installer who supplied the pool, then a qualified fiberglass pool professional. Ask for the maker’s written draining and refilling instructions before the pool is emptied, not after. Refilling belongs in the same plan, because an empty shell is its most vulnerable state.
If a shell is damaged beyond repair, the conversation changes from draining to pool removal and replacement. Our guide to replacing an old pool with fiberglass explains how a replacement project runs, and what affects the cost of removing a pool covers draining as part of a removal quote.
Where can the pool water go?
This part applies to any pool that is drained, whether for repair or replacement. The EPA notes that water treated with chlorine, bromine or salt harms local water quality and is toxic to wildlife and fish when it reaches streams. It also notes that local rules vary. Check with your city or county before water leaves the property.
Two jurisdictions we serve publish clear rules.
| Location | What the official page says |
|---|---|
| Fairfax County, VA | Chlorinated or brominated water can go to a storm drain or stream only after the chlorine or bromine is removed, either by letting it dissipate for 7 to 10 days or by using a chemical agent. The residual must test below 0.1 mg/L and the pH must be between 6.0 and 8.0. The county prefers well-vegetated ground on your own property and calls the storm drain a last resort. Salt pools may not discharge to storm drains or streams. |
| Washington, D.C. | Chlorinated pool water may not go into the storm drain system or public space. It can go to the sanitary or combined sewer in a manner that meets the plumbing code, or be dechlorinated below 0.1 mg/L first. The first-offense penalty is up to $1,000, and it doubles for each later offense. |
For Maryland and West Virginia, contact your local stormwater or public works office. The professional handling the drain should know the local requirements, but confirm them yourself.
What is the safest approach?
- Treat draining as a last resort, and use chemistry and filtration first.
- Contact your installer or dealer before water leaves the pool.
- Follow the pool maker’s written instructions and use a qualified professional.
- Confirm local discharge rules before the water is moved.
Last reviewed October 2026 by Calm Water Pools.
Related guides
- Fiberglass pool care and maintenance
- Fiberglass pool durability and repair
- Pool removal and replacement
- Fiberglass pools FAQ
Planning a fiberglass pool in Maryland, D.C., Northern Virginia or West Virginia? Request a consultation or call 240-372-4440.