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Introduction: We often receive inquiries about how groundwater affects fiberglass pools. In a nutshell, it typically has no impact as long as the pool remains full of water. But what if the pool isn't full? That's where things get interesting.
Understanding Hydrostatic Pressure: Hydrostatic pressure is the term used to describe the force exerted by water on a structure. Excessive hydrostatic pressure can lead to problems, and while it's usually not a concern with fiberglass pools when they're full, it becomes crucial when the water level drops. Fortunately, fiberglass pools often go decades without needing to be drained, but when the time comes, dealing with groundwater becomes paramount. This leads us to the topic of dewatering systems.
The Need for Dewatering Systems: There are three compelling reasons why every fiberglass pool contractor should consider installing a dewatering system:
Efficiency: It's a quick process, often taking less than 30 minutes.
Cost-Effective: Setting up a dewatering system can cost less than $100.
Saves Money and Hassle: It can save you a significant amount of money and the headache of dealing with groundwater-related issues.
Our Approach: Here's how we handle it. After excavating the pool area and ensuring the pool is set and level, we insert an 8” PVC pipe into the ground at the deep end of the pool. The top of the pipe extends above the pool shell and is capped with a skimmer lid, providing instant access to groundwater.
If the pool needs to be drained, simply remove the lid and insert a pump a few days in advance. No need for a permanent pump since groundwater doesn't pose a problem when the pool is full.
Alternative Dewatering Systems: While our method is straightforward and cost-effective, there are other systems worth mentioning. Some rely on suction pumps, like a "mud hog," which draw water from the lower excavation. Although effective, these pumps are bulkier, require priming, and some are gas-powered, demanding regular refueling.
In contrast, our system uses a standard sump pump connected to a garden hose, a smaller and more cost-efficient way to move water. It pairs well with clean gravel backfill, as the gravel acts as a sieve, allowing water to flow freely up through the pipe. With sand backfill, it's recommended to place clean crushed gravel at the pipe's base and drill holes in the side walls, covering them with filter fabric to prevent sand infiltration.
In summary, the choice of dewatering system matters less than having one in place. While groundwater around a fiberglass pool is usually harmless, it's wise to ensure your contractor includes a dewatering solution during installation. It's a small investment that can prevent costly complications down the road.