How much water do you leave on your sun shelf for the winter freeze ?

Rich D

Bronze Supporter
Aug 3, 2018
583
MA
Trying to figure out the best practice for winterizing a gunite / shotcrete pool with a sun shelf. Please post ---

- Depth of water you try to maintain over sun shelf.
- how far down from bottom of tile that water level is.
- how diligently you maintain that level
- type and age of pool surface
- type of winter cover
- any damage you can attribute to winter freeze conditions on the shelf / stairs
And of course anything else that might help others.

The basic question is what depth of water is best to leave on the sun shelf for a winter freeze to prevent damage to plaster? If you leave only a few inches then there will be a a ice brick sitting on the shelf floor for the winter. Or do you drain below the shelf so no ice forms on the shelf?

________________________________________________________________________

- Depth of water you try to maintain over sun shelf.
My pool co. Drained below the sun shelf and told me to maintain that level for the winter.

- how far down from bottom of tile that water level is.
13-14"


- how diligently you maintain that level-
very

- type and age of pool surface
2 yr old med grey plaster

- type of winter cover
do not cover pool in winter but pool tech put a insulated tarp on the shelf for UV and stain protection.

- any damage you can attribute to winter freeze conditions on the shelf / stairs
I probably can not be counted in this category because I am convinced I had a poor plaster install. My plaster has shown far more than normal mottling and is now spalling. Most of the spalling is on the shelf and did occur after the winter but it is happening in other areas as well so I do not think the spalling on the shelf is all from winter damage, instead I believe I just have a week / poor plaster install. The PB has agreed to replace the plaster so I would assume something did go wrong with the install.

The first spring (just after having plaster installed in late fall) everything looked great with the exception of some organic staining under the tarp. I attribute this to some organics that were on the tarp the tech used, so the next year we placed a fresh clean plastic sheet on the shelf then the insulated tarp. I did not get the staining but I did get the spalling .
 
Last edited:

Catanzaro

Platinum Supporter
TFP Guide
Jul 30, 2014
3,403
Monmouth County, New Jersey
Rich:

If you are going to close the pool on your own, then follow the instructions as per the pool company. The reason why you lower your water is that over the winter, the level will rise due to rain and snow. You do not want water freezing on the tiles and cracking them. I work with a liner pool, so slightly different. Each year I lower below the skimmers, but this year will keep at normal levels as I purchased Gizzmo's with blow out plugs. It makes life easier and puts less stress on my TARP cover. Good luck and keep us posted!
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
3,923
Damascus, MD
I don't worry about my shelf at all. My water level is lowered below the returns, which leaves a few inches of water on the shelf. The pool is totally covered with a mesh safety cover. The shelf freezes solid. Never had an issue from this.
 

Rich D

Bronze Supporter
Aug 3, 2018
583
MA
I don't worry about my shelf at all. My water level is lowered below the returns, which leaves a few inches of water on the shelf. The pool is totally covered with a mesh safety cover. The shelf freezes solid. Never had an issue from this.
Great, thanks for the reply... How thick do you think your ice gets ? We can see 6-10"

Ohh.. And what type of plaster do you have?
 

Rich D

Bronze Supporter
Aug 3, 2018
583
MA
Just for reference here is a link to a post where the OP is convinced that leaving a few inches of water on the shelf damaged his diamond brite finish.

 

Rich D

Bronze Supporter
Aug 3, 2018
583
MA
You should keep the water level low enough through the winter so the water does not freeze on the tiles. What other questions do you have?
I guess my original post is a bit confusing. The basic question is what depth of water is best to leave on the sun shelf for a winter freeze to prevent damage to plaster? If you leave only a few inches then there will be a a ice brick sitting on the shelf floor the winter. Or do you drain below the shelf so no ice forms on the shelf.

I am just trying to find out what has worked and what has not worked for others.
 

Catanzaro

Platinum Supporter
TFP Guide
Jul 30, 2014
3,403
Monmouth County, New Jersey
Rich:

You have a concrete pool which is a very strong structure. Having a thick block of ice on the shelf does not make any difference. The key is to keep ice off the tiles. You should have a submersible pump to drain water out if the level reaches to a certain point and that is a few inches under the tiles, maybe 6". This is the experience I have with friends. My pool is a liner, not concrete, but this is what they do. Hope this helps!
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
3,923
Damascus, MD
Freezing damages because it expands and cracks things. It also has been known to damage waterline tiles when they are in the freeze line. Water weighs the same whether it is solid or liquid (the reason melting sea ice doesn't raise ocean levels) so just having ice on your shelf doesn't add anything. Lowering the water level below the tile line and adding something that can be compressed to your skimmers (Gizzmo, gallon jug) is all that is really needed to protect your pool. If ice could damage specific finishes no one in any northern climate would use those finishes, yet they do. That said, you could lower your water level below your shelf if it gives you peace of mind. But depending on how much rain/snow you get over the off-season you may be pumping water out of your pool a lot to maintain that level. For me, my water level is lowered about 12" or so. That is a lot of water before I need to worry about pumping anything out.
 
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