D Maynard wrote:Mark,
You are absolutely correct in your analysis. For a pool less than 5ft deep, a main drain is pretty much useless. The returns do over 95% of the work in circulating the water, with the skimmers and drains doing the rest. The only time a main drain really does anything is when it is placed in the dead zone areas of a pool, and then it is effective. When it comes to liquids and gases, the force of suction force is not effective as pushing the it for mixing.
To illustrate this, all one has to do is put their hand close to their mouth and inhale deeply, then blow back out. Huge difference.
Simply fluid dynamics. I should know. I am a mechanical engineer who does FEA analysis for a living.
If I were a lesser man, I would insult the intelligence of the full of opinion but lacking of knowledge of czechmate, but I believe he has done that quite effectively on his own.
Bravo Mr. mechanical engineer.
Since you so skillfully compared the basic action of a commode to a checking one's bad breath, while you just could not give up the chance to insult my opinion on the basic reason for a main drain, you asked for this reply.
The cleaning of the swimming pool is NOT ABOUT MOVING WATER!
It is rather about most efficiently taking the dirty water AND BOTTOM DIRT, DUST AND DEBRIS to the filter with minimum time, trying to minimize mixing the already cleaned water with the dirty one.
That is why Polaris is still the best pool cleaner out there and still the most expensive.
The time needed to completely clean the pool is called the cycle. It makes difference if it is 4hrs or 8 hrs!
Without main drain it is more like 12 hrs.
Without main drain the bottom dirt, sand, grass clippings, bugs,and other small debris will be just circulating around the perimeter at bottom. Skimmers will be taking in the clean water that the return will bring in at the water top.
So the dirty water including the debris has no reason or is in any way forced to come to the skimmers while I am sucking perfectly clean water back to the filter.
I guess you must be calling this the "Yankee ingenuity", Mr engineer.
Main drain also gives you the additional chance to clean the sand after the sandstorm by closing the skimmers and suck the bottom dirty water only directly to filter.
And i can assure you, the suction at bottom added by pressure of 9ft of water table is more than sucking on your hand or your thumb!( Where you most likely got YOUR GREAT KNOWLEDGE).
BTW, when you get a chance, post a picture how you brush the bottom fine dust toward your skimmers.
I will have it framed.
