I think you're going about this at the wrong end of the "flow train."
If you impede (with a filter bag), or split (with an adapter), one of your returns, all that will happen is flow will be reduced through that return and flow with increase out of your other return(s). The flow will find the path of least resistance.
Ah that's good to know. Well to some degree each return jet (at least in my pool) must have some resistance, as several days ago the microfilter bag was collecting particularly thick amounts of stuff (not from a floc-level accumulation, just more than I thought it'd be), and it burst free from the return attachment. (Never has done so since. I check it more regularly now, it's all settled down and pool crystal clear.) But ok, makes sense if it does distribute it somewhat. Thanks.
And this is good then because it means there's not much to lose by splitting one return jet into two outlet locations, so then the outlet water is more triangulated vs. two spots to one side.
The only way to manipulate what comes out where is if each return has a home run back to the pad (it's own dedicated pipe) with a valve at the pad for each return. Then you could theoretically adjust each return to flow as you want it to. Do you have such a setup?
They both join back to a single outgoing pipe coming out of the chlorinator.
Many folks here, who want finer filtration, use one or both of the following. They'll either add some DE to their sand filter, and/or use a fine-mesh bag in their skimmer basket. Like this or similar:
Yeah, I've done some pool-sock-in-skimmer stuff, but the problem is it's on my only inlet of my pool, so when lots of debris collects (I had a tree scatter tonnes of powdery seeds yesterday), it can strain the pump and damage something. I actually learned this the hard way, where the skimmer basket cracked under sheer force of pump trying to suck water through extremely clogged sock. So now i only use that method if it's hands-on temporary collection while watching pump carefully.
So I'm figuring post-filter collection (in only one of the returns) is superior.
Perhaps there is a skimmer basket/cover hybrid alternative, with an opening to simultaneously suck water through an opening that a basket/sock wouldn't block, anyone know of one? Then I could put a sock in there permanently, check once a week.
As for DE in sand filter I read earlier talks here discouraging, so I haven't tried that. I plan to possibly upgrade to glass filter media as one improvement. Is DE still considered a bad idea or is that assertion out of date?
Also, if you want to fix your main drain, that's fine. But it won't help circulation much. Sucking water out of a pool doesn't do anywhere near as much as pushing water into it. It's the returns that move the water, not the skimmer(s), not the drain(s).
Interesting. thx.
Must be something about the water equivalent of aerodynamics, the pump impeller 'sucks' water through, right, but you're saying the outgoing pushing back in actually makes bigger difference to water flow than the openness of incoming paths?
When I inherited my pool, the returns were just sawed off PVC pipe. They pointed where they pointed. When I remodeled, I had the contractor add eyeball returns. Then I was able to adjust the direction of the flow. That got my pool circulating clockwise, and eliminated all the cold and dead spots. Something like these:
Do you have eyeball returns? Do you have threaded fixtures at the returns that would accept eyeball returns (they thread in)? That's the way to improve circulation. They can be added to a finished pool, with some plaster work, if you're willing to go that route.
Threaded fixtures, thankfully. Thx I'll definitely do something to fix this.
Putting filter bags on returns just isn't done, and two of our resident experts have advised you not to. You would do well to heed those warnings. Improve your circulation and filtering as suggested, but I would leave the returns alone if I were you (unless it is to add eyeballs).
@Bperry Yes that was me. I'm minimising discussion to not catering to alternative chemical solutions now.
Even within just TFP method there can be a lot of variances such as climate or pool debris being significant in in some people's cases.
I think some sometimes people might need a little extra help alongside just the chemical factors. (E.g. they have slightly bad sand in filter and don't have budget to fix it just yet, so a post-filter microfilter bag might be useful for a while, or DE in sand filter, as mentioned.)
