Does pool size influence daily FC demand?

[AW139]

I was trying to think about this. Does the size of the pool have an effect on your daily chlorine loss? I would imagine the same bather load would affect a smaller pool more, but does loss from the sun change with pool size? I ask because I have a small 8000 gallon pool, and I lose between 3-5 ppm per day. Generally around 3.5-4, which seems a bit high. OCLT is passed, and no other issues. Other people talk of only losing 2 ppm per day, and I’m never that low so far this summer.

 

[BDY]

It depends on a lot of factors including shade, bather load, bather habits, organics introduced into pool by nature, the strength of the sun (eg latitude and season) etc etc.

If nothing else Your pool will change over the season as the daily UV changes

 

[Mdragger88]

Peak sunshine/longest days = highest demand
The shoulder seasons are generally the lowest fc demand. Its a bell curve.

 

[mgtfp]

I think the key to answer this, is here:

Thus, the chlorine is most depleted from water near the surface so having good circulation is essential in order to keep chlorine levels more uniform throughout the pool.

Usually pools are made larger by making them longer and/or wider, not really by making them deeper. As long you keep the surface to volume ratio the same, the chlorine consumption measured in FC loss will be the same.

Imagine two identical pools next to each other. They will both have the same FC loss. That doesn't change when you remove the separating wall. But you will of course have to add twice as much chlorine in a pool double the size to meet the same FC demand.

If you make a pool larger by making it deeper (diving pool), then the lower sections of the pool will have a lower FC demand, so that the average FC demand over the whole pool volume will now be lower.

If you make the pool smaller by making it shallower (kiddie pool), then you remove the portion of water with a lower FC demand, so you end up with a higher FC demand for the smaller volume. But in kiddie pools you have usually other "issues" that create even higher FC demand...

 

[AW139]

I think the key to answer this, is here:



Usually pools are made larger by making them longer and/or wider, not really by making them deeper. As long you keep the surface to volume ratio the same, the chlorine consumption measured in FC loss will be the same.

Imagine two identical pools next to each other. They will both have the same FC loss. That doesn't change when you remove the separating wall. But you will of course have to add twice as much chlorine in a pool double the size to meet the same FC demand.

If you make a pool larger by making it deeper (diving pool), then the lower sections of the pool will have a lower FC demand, so that the average FC demand over the whole pool volume will now be lower.

If you make the pool smaller by making it shallower (kiddie pool), then you remove the portion of water with a lower FC demand, so you end up with a higher FC demand for the smaller volume. But in kiddie pools you have usually other "issues" that create even higher FC demand...

That makes total sense. My pool would probably be shallower than average (just goes down to a bit under 6’), so that may explain the slightly higher loss. It stands it’s reason about the lower FC loss as deeper depths.

 

[mgtfp]

Try to get a feel over time how FC demand changes with sun, bather load, season, etc.
Your pool doesn't seem to be really unusually shallow, not sure if I would draw that card here.