Ah, the basin. I have been surprised at all the attention and questions the basin has generated. I would suppose one reason is because our catch basin is in the
front of the pool, e.g. the part that faces you as you look out our living room windows. You bring up a very legitimate point, 18513-Just-a-PB.
I designed the basin for a few specific reasons. The first was so my toddler neices and nephews (and our little dog) could have a safer place to cool off without being underfoot of older swimmers. Second, I did not want a traditional skimmer (in our pool, the basin is the skimmer) because we live on the outskirts of the desert and rabbits, frogs, etc. routinely get trapped in our neighbors' pools and either die in the pool or they find them dead in the skimmer. There are steps in the basin to relax on and also allow an animal or child to get in or out easily. Our dog likes to lay on one of the basin steps (There's about 1-2" water over the top of the step) to get cool.
Now to the basin size. In the beginning, I had no idea what "bather surge" was. I am not ashamed to say I guessed on depth (17") and width (24"). Our autofill is set at 12" from the bottom of the basin. I didn't want the basin to be so wide the toddlers couldn't put their arms out and grab against something and steady themselves (coping, wall) or so deep that they couldn't safely play. I was fortunate to find some articles on this subject during the excavation phase, however, and I realised that I could not have a large sheet of water running into the basin coming from the pool at a sheer angle. That's not what I wanted anyway, I wanted more of a soft water trickle effect. Hence the reason for the angle from the main pool as you see it. When the pump is at full speed the water does not splash out of the basin. We have been swimming since June and I think you are refering to the bather surge which essentialy means for every person that is in the main pool, about 18 gallons of water is displaced and that water has to go somewhere (the basin). When people move around, they displace even more water. This is true. It can get splashy in the basin with kids in the pool. This can ocasionally put a load on the basin to handle. The splashing of bigger sheets of water still go into the basin, but it gets fuller quicker than the pump can handle at low speed. When we are having a party or several kids over, I make sure the pump is going at highest speed and it works fine in this case. I did anticipate possible issues and, being a drainage/utility contractor, installed a massive french drain with a channel drain in the pavers above that to wick away water that does get splashed out by bathers. So far, it's worked pretty well.
In retrospect, I would have made the basin maybe 6" deeper, but no wider. I am not a professional pool designer (obviously) and would encourage everyone who wants a pool with a catch basin to spend consult time and $ with someone who knows what they are doing. I got lucky that this one worked out ok but I had no idea how important different factors are to the basin. For example, wind: wind will displace a lot of water into the basin. When your basin is your skimmer, it helps to put the basin on the predominately wind receiving side (yay! I thought of that!!!), you should have the autofill in the basin only (I've seen a few disastorous stories about pool builders who didn't understand this concept), tile more than the usual 6" because the water level will change (thought of that, too, whew...) etc, etc.
In fairness I should mention that there is a time when I have to really watch the basin. It's when I am vacuuming the pool. I designed all drains to be seperate from the cleaning port, so it's got serious suck-a-luxe. Because the valves are not automated, I have to get them just right (marked it with red nail polish now) to get the pool cleaner going good but not suck the basin dry or overfill it. Normally, only the basin drains and sends it back to the spa only, and the water runs from the spa into the pool, then into the basin like a circle. Cleaning disrupts that circle and I have to make a temporary new circle depending upon what I am cleaning. Example: Cleaning the pool, water goes into the cleaning port and out into the pool and a little goes into the basin to keep it from going dry. I hope this makes sense.
Here is the basin this morning.
I do love this pool and the design definately works for our family. I've got a 1-year-old nephew that is coming over today and he's going to have a blast in that basin.