Can Concrete (Gunite) Pools Float? Crazy Pictures

I was recently sitting with a customer looking to buy a fiberglass swimming pool and the classic question came out.

'Marcus, I was talking with the guy that gave me a quote on a concrete pool and he told me that I didn't want a fiberglass pool because it would float. Is that true?'

I could only sigh upon hearing such a question, as it is one that I figured the concrete pool builders would have gotten weary of using by this point. But instead of expressing my frustrations to this particular homeowner regarding the false words of another salesman, I went on to explain to her the truth, which is as follows:

1. Any vessel, underneath the ground, can float with enough water pressure pushing on it.
2. Of all types of pools, concrete/gunite pools are the most likely to float, as you can see in these photos, all of which are  concrete/gunite pools.
3. Fiberglass pools, although potentially could float if they were empty of water or had no concrete decking bond beam, almost never float.

Hydrostatic pressure, or water pushing upwards, is the reason why pools can pop up out of the ground. To alleviate this problem, the majority of concrete pools are built with a hydrostatic relief valve. In the case of fiberglass, as long as they remain full of water, and have a cantilevered concrete coping edge around them of at least 3' (this is our general rule of thumb at River Pools), then floating should never be an issue.(See Jason's recent article regarding hydostatic pressure and fiberglass pools)

After having literally installed a few hundred pools on the waters of Virginia and Maryland during our time in business, we have not had one of these pools pop-up or 'float' after installation. In fact, the only case that typically leads to hydrostatic issues with a fiberglass pool is when they are drained/emptied of their water, which is an absolute 'no-no' and can cause, instead of the pool floating, the pool's floor to buckle or crack. Such can be repaired, but is obviously not a good thing, which is why fiberglass pools should always remain full.

But remember this the next time a concrete pool salesman has the audacity to use the old 'fiberglass pools float' pitch. In fact, if you're in the process of buying a pool and getting quotes on both concrete and fiberglass, then I suggest having these little pictures handy in case the subject happens to come up. :-)

As, always,happy swimming to everyone and if you have any questions or comments, please don't hesitate to leave your thoughts below.

Marcus Sheridan, PoolSchool