One inlet or two?


Well-known member
Mar 20, 2021
Las Vegas, NV
I have three inlet valves (skimmer, main drain and cleaner). For as long as we’ve owned the pool we’ve only ever had the “skimmer” valve open. It’s the way it was when we got here and we’ve just never touched it. Question is - is there a good reason to also open the main drain valve? The cleaner valve has a cap on it in the side of the pool that only gets opened if we attach a vacuum, so that one doesn’t pull any water in, even if the valve is open.


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

There are thousands of pools out there without operating main drains and they all work just fine.. But, it is nice to keep the water in the pipes fresh, so I'd set it to run at about 5 or 10% open and the skimmer line fully open.

Obviously, if it has been closed for years, you already know you don't need to run it if you don't want to..


Jim R.


Well-known member
Mar 20, 2021
Las Vegas, NV
Just to make sure I’m clear, does the main drain pull water in from the circle grate at the bottom of the pool? And when you say 5-10% open, do you mean just shift the valve a little bit so it isn’t closed tightly?


Gold Supporter
May 20, 2020
Katy TX
Pool Size
Liquid Chlorine
Some pools do not even have a main drain so in that regard you really do not need to open it. However since you have it, it does provide a deep water circulation path and an alternative should your skimmer malfunction or your water level drop (you would need to turn off the skimmer to prevent air from entering the pump).
One concern I would have, if it has been closed for a long time with no circulation, algae could be in there. However, once you open it you can ensure you have good chlorinated water circulating through it. I run my pool with 80% open to skimmers and 20% open to main drain. The only time I have put it on 100% main drain is when I did a partial drain and as I was refilling the pool I had it on 100% circulation through the bottom drain until water level reached the skimmers then switched back to dual skimmer/main drain suction.
Similar to main drain, if you have never used your suction side cleaner, leave the cap on it in the pool connection.
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