Water Level Band for Vinyl In-Ground Pool

[goody222]

I'm trying to figure out what my minimum and maximum pool level band should be. I'm surprised I can't find any official information on this. So my Hayward skimmers have a tiny, faint arrow for proper water level. About 1 inch above that is a screw holding the skimmer in on each side. My pool builder recommended that I maintain it around the screw level (that way I can just look out the window too see water level, plus I can let water level drop during a dry spell before refilling).

For Maximum level = I was advised not to let it get to the top row of 4 screws, which is pretty high. What is the problem with level too high but not high enough to overflow the pool - this 'floating the liner' I've heard about?

For Minimum level = No idea on this one. I know if it gets too low the pump will start to pull in air which can damage the pump, but I'm not sure how low to go.

One reason I ask these questions is that I'm in a hurricane zone, so before we get 8" of rain with the power out leaving me unable to drain the pool, how far can I drain the pool? My pool builder said I could close the skimmer valves and drain to below the bottom of the skimmer before the storm. Thanks!

This is or is very close to my skimmer = Amazon.com : Hayward SP1084 Auto-Skim In-Ground Pool Skimmer, Square : Swimming Pool Skimmers : Garden Outdoor

 

[_Stang]

I have the same skimmer and keep it at the 3rd screw. If water level gets above the skimmer it will pull water in but never skim anything off the top (bugs, etc). Too low and you'll pull air into the system.

 

[PoolGate]

Plus 1 on Stang. If the level is too high you can see the door on the skimmer will not allow anything but (mostly) just water to pass. This means leaves and bugs and stuff will not be picked up by the skimmer. I run mine slightly below the "recommended" level because I get much better skimming action. I have plaster though.

 

[Yev]

All responses so far are spot on.
2nd screw from bottom should be absolute minimum to prevent air getting to pump
3rd screw from bottom should be max or skimming wont occur.
Mid way between the 2 is the default level, but you can adjust slightly for your own pool.


Teh trick to all of this is to understand how the skimmer works. There is a door inside the skimmer, called a Weir Door, that angles back into the skimmer. This is angled so that debris can float in, but not get out (If the door were perfectly vertical, debris would run into the door, adn rather than just going over the top, it would bounce off the wall back into teh pool). They way this happens, is that there is a float attached to the inside of the door, that keeps the door even with the level of the water INSIDE the skimmer. IF the pump was NOT running, then the level of the pool water and the level inside the skimmer would always be the same.

(I am going to explain this next part with a lot of words, so it might seems like along slow process. It is important to note that this is happening in fractions of a second)
When the pump runs, the pump sucks in water from inside the skimmer. If there were no Weir door, then the pool water level and the skimmer water level would stay level. But since the door blocks about 90% of the water flow into the skimmer, something interesting happens. The water level inside the skimmer drops down below the level of the pool. Since the door floats at the level inside the skimmer, the door angles down even further. When it does this, it creates a wave of water that crashes over the top of the weird door. WHy does it do this, water will naturally want to make both levels of water equal. As the water crashes over the top (think a wave going towards a beach and a surfer riding the wave) it picks up momentum, and carries debris aggressively into the skimmer. And just as it does this, it raises the water level inside the skimmer, and therefore puts up a blocker to prevent the debris from going back into the main pool.

Now the process repeats, and the pump draws the water, and the newly deposited debris down into the skimmer basket.

This whole process repeats constantly when the pump is running.

So I tell you all of that to say this. Getting the water level right will GREATLY effect the skimming and therefore cleanliness of your pool. So figuring out the ideal level will take some trial and error of you watching how well things get sucked into the skimmers.

But, with all that said, you then need to account for pool water evaporation. Your water level will slightly drop everyday unless it rains. So you can quickly go from an ideal level to one that is too low.

For my pool, I know right where the sweet spot is, but when I get rain, I leave my pool level high (at the 3rd screw) rather than pump it down to the ideal level. I do this to conserve water usage. I know it isn't skimming as well, so I just spend a bit more time manually skimming on those days.

 

[goody222]

thanks for the explanation! That's what I'm doing right now also - max out at the 3rd screw, then let evaporation happen.

I guess part of my question for absolute min and max level is for a really big storm/hurricane that is about to drop several or more inches of water - so how far down should I pump it and/or how high can I let it go before I HAVE to pump it down.

 

[Yev]

Someone may have a more exact instruction set that me, but here are my comments on your situation. You dont want the water to reach the top of the liner, where the liner snaps into the pool wall right under the coping. So if they estimate your rainfall, I would drain the pool down far enough to make sure that you dont think that you will hit that liner top. If this is much below the 2nd screw, then you might want to turn off the pump while the storm passes to make sure that you don't get air in the system.

If this were my pool, this is what I would do. My pool has 2 skimmers and 1 main drain. Each has a valve right before getting to the pump. I would shut off the valves for both of my skimmers, meaning that my pump would only be drawing water from the main drain. I would then drop the water level down a bit more than they predict (They predict 12 inches, I drain down 15). The whole purpose of this valve adjustment is to make sure that if the water level gets to low no air will be drawn in from the empty skimmers. I would then probably turn off the pump until after the storm passes, and just deal with the debris then. If during the storm the water level approaches the liner top, I would turn the pump back on and pump water out of the pool with my backwash setting.

 

[goody222]

Yev, Thanks - makes perfect sense for short term events like a bad storm.

 

[Yev]

One option I did not say, is that you could keep the pump operating with only the main drain open which will at least keep teh water beign filtered and chemicals stirred in, even if the skimmers wont be doing anything. I guess it all depends on how bad the storm is predicted to be where you are at.