Help! My pool liner is floating.

 Spring is around the corner and like most homeowners you can't wait to get your backyard in order and ready for summer.  Spring means rain, rain and more rain.  Usually after multiple rainfalls or one big rain we get a very common phone call.  Help!  My vinyl pool liner looks like it's floating!

Vinyl liner bubbling in from wall.

Vinyl liner floating.

First and foremost, this is a common occurrence in the Spring and your pool isn't the first to experience it.  Take a deep breath, the vinyl pool liner will eventually go back into place without damage.  So why is this happening to your vinyl pool liner?

Being located in Central Indiana, the water table underground can create hydrostatic pressure underneath your swimming pool.  Typically during the Spring you will see the ground water table rise due to snow melting and spring rain showers.  If your backyard or surrounding areas have some standing water or easily become swampy, your water table is very high.  This affects your backyard swimming pool because that high groundwater table or hydrostatic pressure is pushing up on the bottom your pool.

So hydrostatic pressure is created when the groundwater outweighs your pool water.  The groundwater will then push upwards to relieve the pressure. This gives your pools vinyl liner the appearance of floating, bubbling or a blister.  The upside to a vinyl liner in-ground pool is that after the groundwater resides and your liner drops back into place, it may leave you with a few wrinkles.  These wrinkles can be an eyesore but do not damage the integrity of the pool. If your pool was constructed with a concrete or fiberglass, the hydrostatic pressure could lift and break the concrete or fiberglass bottom, creating a major issue.

Pool coming up out of ground due to hydrostatic pressure.  

So how do vinyl liners survive hydrostatic pressure when concrete and fiberglass pools are damaged by it?  Vinyl liner in-ground swimming pools are typically constructed with a vermiculite bottom or base.  Vermiculite is a porous base that can keep its form similar to concrete.  But being porous allows the ground water to pass through it.  This helps keep your in-ground pools floor intact with no damage.

Owner, Tom Murr troweling the bottom of a pool with vermiculite.

So next time your vinyl pool liner looks to be floating, keep as much water in the pool as possible!  The more water in the pool, the more pressure to keep the ground water from rising higher.  Look into installing a sump pit if your liner floats multiple times a season and want to help alleviate the problem.  This can help ease the high ground water problem by moving the water away from underneath your pool.

Talk with your local pool builder professional about any issues, concerns or solutions you may have regarding a high water table in your backyard.