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Deborah, Gardening Enthusiast
Category: Home Improvement
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Experience:  Past Community Garden Club President, Decorating & Home Improvement, Martha Stewart & Bob Vila Fan
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how long can you leave a pool unfilled with water

Customer Question

in ground gunnite pool
we ae getting work done around pool and it has been drained, we were told it will crack if we do not fill it with water in a day or so, we ae in new england
Submitted: 9 years ago.
Category: Home Improvement
Expert:  Deborah replied 9 years ago.


I am in CA and have always maintained an inground pool.

It all depends on whether there is ground water on the other side of the gunnite shell and how deep it is. Assuming the pool is 15 x 30 feet with a 4 ft shallow end and an 8 ft deep end and is rectangular, not rounded: the weight of the gunite would be approx. 87,000 lbs (6 [email protected]/cc). An equivalent weight of water would fill the deep end pool plus another foot. If the ground water exceeded that level on the other side of the gunite the pool would pop out of the ground and float on whatever level water you have. If you drill a hole through the bottom or side of the pool 1 or 2 feet from the bottom the lift pressure will be relieved as water comes out and you will have no worries. Gunite is very strong and the pool can remain empty quite a while if there is no: water, land movement , earthquakes, or other mechanically damaging prospects.

Deborah, Gardening Enthusiast
Category: Home Improvement
Satisfied Customers: 3217
Experience: Past Community Garden Club President, Decorating & Home Improvement, Martha Stewart & Bob Vila Fan
Deborah and other Home Improvement Specialists are ready to help you
Customer: replied 9 years ago.
Reply to Deborah's Post: Hi Deb

I think you misunderstood my question. This is an existing pool so we know it will hold up where it is. We want to know if the plaster coating on the pool's surface will crack if it is exposed to direct sunlight. Our pool person says we should fill it with water right away to avoid tiny spider cracks; we're still having work done around the pool area so we were going to wait to fill the pool. Can a pool sit exposed for a set amount of time? Please advise.

Expert:  Deborah replied 9 years ago.

That is true as well, however, if you have an empty pool and high ground water table in your area and should your region experience heavy rains, the ground water can create pressure on the walls of the unfilled pool and create damage. It is important to know what the ground water status is in your region when draining your pool.

That is the biggest worry. My parents live in NJ, drained their pool to have work done on it. Heavy rains came, ground water level increased... pool "popped" a nice size crack.

It is bet to refill the pool as soon as possible, there are no minimum or maximum guidelines; however, the longer it remains empty, the more room for damage.


Customer: replied 9 years ago.
Deborah--Again, we're not worried about water tables. We simply want to know if gunite exposure to the sun without water in it will create lasting damage. Do you have any information on that? Thank you.

Expert:  James replied 9 years ago.


I would stronly recomend filling the pool at least half way for now. But YES it definently needs to be filled or the Gunite will crack excessively. I would recomend doing this as soon as possible. For further reference. Never allow your pool to be completly drained for more then 2-3 days. If longer then that time frame you are at risk for serious damages.

Hope this has helped. If so please click the green accept button next to this post.



Expert:  Deborah replied 9 years ago.

Yes, sun and other evironmental elements can cause drying, flaking and cracks when a pool is left drained.

It is however, most important not to underestimate the potential for wall damage and cracks due to pressure applied on the walls related to ground water. This factor is extremely important even in existing pools. Any reputable pool construction firm or pool maintinance company will not guarantee you a crack-free pool if your groundwater source isn't completely controlled prior to undertaking any pool draining efforts..

My son-in-law's family owns a large pool construction firm and upon consulting with him, he has mentioned that a pool should only be drained in urgent situations. It is never recommended to completely drain the pool. He suggests 10-14 days is the max and only recommends this to his clients in situations that are beyond their control. However, there are no guarantees. The age of the pool is also a mitigating factor. The older the pool, the more chance for cracking.

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