Are All Main Drains Created Equal?

[cleancloths]

Here is a picture from the above page:



with a cover like this it would be almost impossible to have an accident like the one talked about.

[elsie]

Thanks all. I understand better now. The cover by definition, contrary to what I was thinking, does not necessarily preclude water intake, but rather by design mitigates the intake as I see in the picture (depending on the situation with the valve below it). And that's just how my cover looks, although I'm not sure I can visually see those vertical sides, but I do see the plate and screws.

It would be interesting to know the history, i.e., why mine does not function as part of an integrated whole. Maybe a leak as suggested. It's also worth noting that apparently whether or not that main drain is completely closed off or not doesn't seem to affect the efficiency of water circulation, or problems associated therewith. Of all the posts I've read, I've never read "yeah, my main drain is closed because the valve leaks so I don't get good circulation and tend to get algae."

So back to a chicken-and-egg thing, if the circulatory system works fine without use of the main drain, why did they install them in the first place? And do they still?

[cleancloths]

There is a lot of arguement as to if they are needed or not. In a "Perfect" engineered design you probably don't need one. But, most pools are far from perfect and having one will improve circulation and help maintain a much more steady temperature. Remember that heat rises, so the bottom of the pool will tend to be much colder. By pulling the cold water off the bottom you mix it better with the pump and eliminate thermal gradients in the pool, not to mention circulating chemicals better.

If there were no reason for them you can be certain contractors would not install them as they cost money.

[elsie]

I think the pic Cleancloths posted is mine:

Sta Rite 8" Anti Vortex 0712-0741

Manufacturer: Sta Rite

Maximum Flow, ANSI/ASME A112 Rating
60 GPM

This cover is A112 approved at 60 GPM

The Sta Rite cover is flat on the top with a circle in the center. Water is drawn in on the elevated sides..

_________________

If the valve were open, I would not be able to feel water being pulled in? SO maybe mine is open after all? I'll dive down this weekend with a vial of dye to see, just for the heck of it.

[Rangeball]

I have an 15+ year old 16'x32' IG vinyl liner pool, 3.5' shallow end and 8' deep end. One skimmer, one main drain centered in the deep end and one return paralleling the 16' side in the shallow end. With only one return it needs the main drain to ensure adequate circulation, and I run both the main drain and skimmer wide open, closing the main drain only when vacuuming to maximize suction.

My main drain has a circle grate cover. The actual 1.5" outlet is in the side of the "bowl". Although you can feel the flow when you cover the grate with your hands, it is well dispersed since the cover is 8" from the 1.5" outlet so suction is minimized. I can't imagine anyone getting stuck to it.

[elsie]

I guess the cover would have to rupture somehow (earthquake, or a shift in the ground), then depending on the GPM, it could hold a person to it?

How in the world do you close that drain to vacuum without diving down and manually closing it?

[Rangeball]

There is a valve before the pump that shuts off the main drain line.