I'm a pool professional who's been dealing with a pool with high demand for years. The pool is just over 40K gallons. There's a spa attached to the same system as the pool that's just under 1K gallons. Sanitation is provided by an IC60. During the heavy parts of the swimming season, I have to run the generator at 100% while its in pool mode and 20% when it's in spa made. I have the spa set to run for 5 hours from 7p to midnight, and then it runs on the pool the rest of the time. I have a very hard time keeping the chlorine levels at the 7.5% of the CYA level on this pool. I have to manually add Sodium Hypo every week to both bodies of water or the chlorine levels just keep falling. The pool gets used A LOT. They basically open their pool up to their church and people from the church use it often, so the bather load is very high. I know I don't have some sort of biological issue, because this is only an issue when school is out. Once the use of the pool goes down, I have no trouble keeping the FC up where it should be and can turn the generator down to more reasonable levels. Because of the way the pool builder designed the equipment pad, adding any sort of additional chlorine feeder is difficult. Currently, there's no room in the plumbing for an additional SWG, and because the equipment is below water level and the single pump nature of the design of the system, I'm not confident in accurately controlling the FC with a liquidator.
BUT, due to issues that don't need explained at length here, I'm going to be replumbing the equipment pad to fix some hydraulic issues the builder created in the way he built the system and installing a variable speed pump and eliminating a second pump the builder was using to run half the spa. Also, because the builder didn't put any kind of equalizer line in-between the pool and spa, the chemistry is often different in both bodies of water and I basically have to treat them separately.
So, here's my question; What can I do to either increase the chlorine generation in the pool, or reduce the chlorine demand? My local Pentair rep is pushing Bioshield, but I'm well aware of how UV is looked upon in outdoor residential pools on this forum. I will say that this pool has an automatic cover and it's kept closed a lot, so maybe the UV would help reduce the demand enough that the SWG could keep up? Since I'm replumbing the entire equipment pad, I'll have the freedom to do as I please for additional sanitation now. My initial thought was to add an additional SWG and have one run at a fixed level and the other controlled by the automation. I'm concerned that if I turn it down enough to work with the spa, it won't do enough for the pool. I'm pretty confident that I can't have both of them controlled by the automation system without upgrading the control board in the automation (It's an old Easytouch8), but I think that's going to be a hard sell due to the expense, plus Pentair is phasing out the EasyTouch8 and wants us to upgrade the boards to the new IntelliCenter systems. As I've said before, I'm concerned about the liquidator working due to the equipment being nearly 6' below the water level in the spa, and 3' below the pool water level. I'm also concerned about control since there's no equalizer line, trying to get it set to a level that works for both bodies of water seems impractical.
I'd love to hear any ideas anyone might have for how to deal with this.