Possible Causes of a Vertical Crack Near the Main Drain of a Fiberglass Pool

Poor Compacting

• As the central drainage area for the pool, the main drain connects to a series of drainage pipes that help direct water, dirt and other debris from the pool for effective sanitizing. During a fiberglass pool installation, soil from the excavation can surround the pipes as the backfill is set into place. If the soil is not properly compacted prior to adding gravel or sand backfill, it may exert excessive pressure on the pipes. The pipes may then transfer the pressure to the fiberglass shell near the main drain and cause it to crack. To avoid this type of damage, hire an experienced fiberglass pool installer who will not rush the installation or cut corners.

Improper Leveling

• Your fiberglass pool may develop a vertical crack near its main drain if the pool shell is not properly leveled. Getting a fiberglass pool perfectly level is very difficult because the material is malleable and the terrain in your backyard may not lend itself to a completely level hole for the excavation area. Once you add the backfill material and put water in the pool, it is normal for a fiberglass pool to be up to 1 inch out of level in a 40-foot area, according to River Pools and Spas. When a pool is more than 1 inch out of level, installers may sometimes try to level the pool shell itself if they are unable to adequately adjust the pool’s base terrain. Continually lifting the pool out of its excavation hole and repositioning it can put a significant amount of pressure on the fiberglass shell, particularly in the center area of its deepest portion where the main drain is typically located. Under this pressure, a crack may develop immediately or occur over time. In order to avoid a crack as the result of improper leveling, verify that your pool manufacturer produces pools that are level and work with an experienced installer.

Obstruction in Pool Floor

• Problems can occur with a fiberglass pool installation due to the terrain of the excavation site. In some cases, however, these issues may be avoided if the site is properly prepared before the fiberglass shell is set in place. If your installer leaves any rocks, masses of dirt or tree roots that may jut up into the pool floor on the bottom of the excavation site near the main drain, these obstructions may provide enough pressure against the fiberglass shell that a vertical crack develops in its gel coat. As with the other crack causes, you can avoid this type of issue by checking your installer’s references to ensure that he is known for thorough, quality projects.

Improper Drainage

• Even if your pool is properly installed, a vertical crack may develop in the fiberglass shell near the main drain if you empty the entire pool of water. A fiberglass pool is not designed to be completely drained because, if the proper procedure is not followed, ground or hydro-static pressure can strain the shell and cause a crack. When winterizing your pool, lower the water level to just below the skimmer to avoid these issues. If you must drain the pool completely, consult your pool’s manufacturer or installer to determine the proper procedure for emptying it.