We've had a lot of people using the tub this summer, way more than usual, and I'm staying on top of the water but I feel like I'm chasing my tail with sanitizer between sessions. I'm shocking after every heavy use night, but by the next afternoon the FC is still lower than I'd like before people get back in. Curious if anyone has settled on a good routine for high-bather-load weeks, specifically whether you're dosing more frequently throughout the day or just leaning harder on the overnight shock. I've been keeping my cyanuric acid on the lower end since we're indoors under a cover most of the time, not sure if that's working against me here.
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Hot tub getting hammered with summer parties - keeping up with chemistry
- Thread starter NC_Nick
- Start date
Same situation here, first summer with the tub and way more people in it than I expected. One thing I picked up from reading around is that shocking right before bed means the water doesn't have enough time to work through it before the next afternoon, so if you can shock earlier in the evening it might help. Not sure if that's your setup but it made a difference for me.
NC_Nick, the issue is almost certainly oxidant demand, not just sanitizer demand. Heavy bather loads dump a ton of organic waste into the water - sweat, sunscreen, body oils - and all of that consumes your free chlorine before it even gets to actual sanitization. Shocking after the fact helps, but you're always playing catch-up if you wait until after people get out.
What worked for us when we started running the tub hard on weekends was shifting to a pre-event shock the morning of, giving it several hours to gas off and restabilize, then doing a smaller maintenance dose an hour or two before anyone got in. That way you're not starting from a depleted baseline. The evening shock after everyone's done is still worth doing, but if your FC is reading low by the next afternoon it usually means the overnight shock didn't fully burn through the organics before it dissipated.
Also worth checking your CYA level if you're in a covered spa and using trichlor or stabilized tablets as your regular sanitizer - it creeps up over summer and starts blunting how effective your free chlorine actually is. I'd also pull a full panel and look at your phosphate levels if you haven't recently. High phosphates won't tank your FC directly, but they can point to a heavier organic load in the water than you're accounting for. If you're already on top of all that and still seeing the drop, the short answer might just be more water changes - dilution fixes a lot of sins when the tub gets hammered for several weeks straight.
What worked for us when we started running the tub hard on weekends was shifting to a pre-event shock the morning of, giving it several hours to gas off and restabilize, then doing a smaller maintenance dose an hour or two before anyone got in. That way you're not starting from a depleted baseline. The evening shock after everyone's done is still worth doing, but if your FC is reading low by the next afternoon it usually means the overnight shock didn't fully burn through the organics before it dissipated.
Also worth checking your CYA level if you're in a covered spa and using trichlor or stabilized tablets as your regular sanitizer - it creeps up over summer and starts blunting how effective your free chlorine actually is. I'd also pull a full panel and look at your phosphate levels if you haven't recently. High phosphates won't tank your FC directly, but they can point to a heavier organic load in the water than you're accounting for. If you're already on top of all that and still seeing the drop, the short answer might just be more water changes - dilution fixes a lot of sins when the tub gets hammered for several weeks straight.
The pre-party bump that soaklife mentioned is probably the single most useful thing you can do, but I'd also add that the timing of when you test matters almost as much as what you add. I got into the habit of testing right before anyone got in, not just the morning after I shocked, and it changed how I managed things. If you test at noon and people are getting in at 3, you actually have time to top off FC or give it a quick boost before the load hits.
The other thing worth paying attention to is total dissolved solids and combined chlorine building up faster than normal over a heavy-use stretch. When you've got a lot of people in and out over several days, even if your FC looks okay, the water can start to feel off and work less efficiently. I'd do a full panel midweek during a stretch like that, not just check FC and call it good. Drain and refill start to become necessary more often when the tub is working hard all summer, and it's easier to get ahead of that than to fight water that's just worn out. I think a lot of people underestimate how quickly TDS climbs with high bather loads, especially in a smaller volume of water like a hot tub.
The other thing worth paying attention to is total dissolved solids and combined chlorine building up faster than normal over a heavy-use stretch. When you've got a lot of people in and out over several days, even if your FC looks okay, the water can start to feel off and work less efficiently. I'd do a full panel midweek during a stretch like that, not just check FC and call it good. Drain and refill start to become necessary more often when the tub is working hard all summer, and it's easier to get ahead of that than to fight water that's just worn out. I think a lot of people underestimate how quickly TDS climbs with high bather loads, especially in a smaller volume of water like a hot tub.