Something I've always wondered

Buggsw

LifeTime Supporter
Apr 22, 2007
925
Arizona
I have an IG pool with a drain in the floor and a skimmer in the side wall of the pool. In the bottom of the skimmer (under the skimmer basket and under the other spaceship looking gizmo - which is a technical term), there are 2 holes. One hole I know is the suction to the pump and where I plug in my vacuum hose. What would the other hole be?
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,629
SW Indiana
If it's open, it's the line for your your main drain. Both return to the pump through the skimmer line. If it's plugged, your main drain has its own line to the pump.
 

Buggsw

LifeTime Supporter
Apr 22, 2007
925
Arizona
JohnT said:
If it's open, it's the line for your your main drain. Both return to the pump through the skimmer line. If it's plugged, your main drain has its own line to the pump.
Thanks for responding John. So, you mean the main drain has 2 lines back to the pump? I'm a little confused about the "If it's plugged..."
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
32,863
Sebring, Florida
Hi, Buggs,

John is saying that your main drain and skimmer may be hooked in "series". In other words, if both holes are open in the bottom of the skimmer, one of those holes connects the main drain to the skimmer, the other one connects the skimmer to the pump. So water from the main drain first passes through the skimmer before returning to the pump.

If one of the hole is "plugged" (normally with a pvc screw cap that has a square top) that is not the case. Your main drain then would be connected directly to the pump and not pass thru the skimmer.
 

KurtV

LifeTime Supporter
Mar 29, 2007
270
SE Louisiana
duraleigh said:
Hi, Buggs,

John is saying that your main drain and skimmer may be hooked in "series". In other words, if both holes are open in the bottom of the skimmer, one of those holes connects the main drain to the skimmer, the other one connects the skimmer to the pump. So water from the main drain first passes through the skimmer before returning to the pump.

If one of the hole is "plugged" (normally with a pvc screw cap that has a square top) that is not the case. Your main drain then would be connected directly to the pump and not pass thru the skimmer.
Buggs,
There are at least three ways to plumb skimmers. As Dave said, the second outlet in the skimmer can be tied directly to the main drain line. Alternatively, a single outlet in the skimmer (with the other being plugged) can be tied to the main drainline via a diverter valve that's buried beneath the skimmer and is used to regulate the flow between the two (e.g. divert all or most of the flow to the skimmer for vacuuming). Finally, the skimmer and main drain can have separate lines that each have their own shut-off valve and are joined after those valves and just before the pump.

The third is the setup I have. It has the disadvantage of making it easy for you shut down the main drain valve and then, if the skimmer(s) get clogged or the water level drops too low, run the pump dry. I guess the second option has the same problem.