Suction: skimmer vs skimmer + main drain?

[tomfrh]

I have an older pool which sucks primarily from the skimmer.

The main drain leads to the side of the skimmer. It sucks a small amount via the skimmer, presumably via Venturi action. I’ve put dye in the main drain to see the flow rate, and it’s very low.


our previous pool (which was newer) had separate suction lines from main drain and skimmer, which obviously sucks a lot more thru the drain.


im considering replumbing my main drain to a separate line to get more even suction, better mixing, and greater control over the system.

Any thoughts?

And whats the logic of main drain running to the side of the skimmer as opposed to its own line?

 

[Jimrahbe]

Tom,

I have two rent houses with main drains tied into the skimmer. Neither one has a operating main drain. At my house, which is newer, the main drain is plumbed back to the equipment pad.

I can't tell any difference in the way the three pools operate. I only run my main drain at about 10%.. If for some reason it quit working today, I would not spend a penny to fix it.

There are thousands and thousands of pools with no main drain, or no operating main drain, and they all work just fine.

Not sure what problem you have that you want to blame on the main drain, but whatever it is, it is unlikely that the main drain has anything to do with it.

Thanks,

Jim R.

 

[tomfrh]

I feel it would filter and mix a bit more evenly if sucking through the main drain. As it stands the bottom of the deep end is a bit of a “dead zone”, filtration wise. I get a cold layer there, which suggests limited turnover of water at depth. When I put the food dye next to the main drain it just sat there without dispersing. The drops at higher levels mixed quickly.

dont get me wrong, there no real problem as such. The pool looks good. It’s clear. But it troubles me to think part of my pool water is not turning over at the same rate as the rest of the water. Particularly when the bottom part of the pool is where particles are more liable to settle.

 

[tim5055]

I'm a fan of a min drain plumbed back to the equipment pad. But, with that being said I don't know if in your position I would tear things up just to re-plumb it. If it was [art of a bigger project then yes, I would do it.

I don't know what skimmer you have, but many that work like you describe have a disk under the skimmer basket that allows you to adjust the amount pulling from the skimmer vs the amount pulling from the main drain line. This is a part that many times is removed by previous owners and leaves them in the position you are in. Just a possibility.

 

[tomfrh]

Tim,

yes it has the disc to balance the flow. Same disc I use to vacuum the pool.

i don’t really like this as a method to balance it. It’s quite clunky.


the main drain plumbs to the side of skimmer, opening just above the basket.


there is some easily removable paving here, so I could access easily enough.

there is also a redundant 32mm line for pressure cleaner right next to the skimmer, running back to the equipment, which could function as a main drain line.


i grew up with a pool that had separate lines for skimmers (there were two) and the main drain. To my mind this is how it ought to be.

 

[KDpoolguy]

If you have the time, access to the pipe, and desire, I’d say it’s worth it. I had a similar setup, and suction mainly thru skimmer, until I realized there was supposed to be a diverter float at the bottom of the skimmer. Not for nothing, but maybe there is something at your skimmer that was removed (like mine and others with a U3) that can direct more suction from drain?

Before the suction was more adequately shared, I had more chemical usage and poor circulation and cleaning (I have an in floor cleaning system) and worse heat distribution. For those reasons, that you may not realize until later that more drain suction is a good thing.

 

[tomfrh]

Kdpoolguy,

thanks. It’s good to hear it makes a real difference.

ill have a better look at the skimmer to see if I’m missing anything. Otherwise I may replumb separately. I intend to own this pool for many years, so may as well do it.

 

[Mayorb]

I service pools with and without main drain lines to the pump.
Overall I have seen no difference in the functionality of these systems. A pool cleaner basically acts as a roving return or suction line (depending on type) so circulation is not a big issue.
However there are two main benefits to having a designated suction line from the drain;
1. Dust and dirt can be swept into the drain directly, and be pulled up into the filter.
2. The system can run in low water conditions by cutting off the skimmer(s) and isolating the main drain suction until the pool is filled.