Trying to Decide on Hot Tub Filtration

[mayberry32]

Installed a new saltwater pool several years ago and love how easy it is to maintain. Also love the feel of the water. We did not put a spa in when we built the pool, because I've never liked the functionality of a built in spa with a pool. I much prefer a stand alone hot tub. I also wanted it closer to the house, under our covered deck, so it could be used easily even on rainy days. We are to the point I'm looking at new and used hot tubs and I'm trying to decide on a filtration system. I've searched in the search bar here and can't seem to find what I'm looking for. Is there any overwhelmingly preferred system for a hot tub?

I've seen where salt is more buoyant (which is sometimes not preferred in a hot tub), and where the SWG will send the chlorine very high, if the tub is covered or not used for a period of time. I've also seen where some people worry about corrosion and longevity with a saltwater hot tub.

I've also seen people say bad things about the FROG system, and adding liquid chlorine to a hot tub.

I'm sure all have their plusses and minuses, but I'm looking for the best feeling, easiest to maintain, and most enjoyable. Balancing my pool chemistry is nearly nonexistent. I add maybe a bag or two of salt per year and muriatic acid maybe once or twice a year. That's about it. I love that about the saltwater pool. I'm open to anything, but I need to narrow my search and I'm just looking for advice. My pool is 36,000 gallons and a hot tub is closer to 400 gallons and has to be drained several times a year. So, I'm just confused about the best system to go with. Any advice or opinions are welcomed and appreciated.

 

[Texas Splash]

Let's see if @RDspaguy can help give you some shopping tips to consider.

 

[cranbiz]

The Frog system does work and it's easy to maintain, it's expensive to use. Some don't believe it's the best system and that is probably true. It's not "smart" it's time delayed chemical disbursement.
Dichlor and liquid chloring is a better system of sanitization. It works but it requires more effort on your part but it's also inexpensive to use.
A SWG is more cost upfront, eventually will require a fairly expensive salt cell replacement but is again an easy system to maintain. Something like the Saltron mini, which is a drape over the side device, is reasonably priced and the replacement cell (which appears to last a couple of years) isn't ungodly expensive.

No matter which system or sanitization you go with, you will need to drain and purge your tub every 3-6 months to get rid of nasties that accumulate as a byproduct of sanitization.

 

[Ahhsomeguy]

SWG’s are great for hot tubs. I strongly recommend using one, especially in hot tubs and swim spas that get moderate to heavy use. An ideal program for all hot tubs would be to use the weekly maintenance product Aqua Clarity. Aqua Clarity will be your backup quarterback when and if the free chlorine level bottoms out periodically.
your water will maintain perfect clarity. One major reason for using the productmis that you won’t need to purge and drain nearly as often. The Aqua Clarity sweeps away bio-gunk 24/7 from surfaces. Since biofilms has a hard time attaching and colonizing when using it, your filter system grabs much of it. Using a salt water generator with the “AC” product is a very smart thing to do.

 

[mayberry32]

Thank you for the replies. My hangup with the SWG is that it's a $1600 upgrade and I was told by the spa dealer that you can't use regular pool salt in it. It requires a special small bag that's $25 for what looks like 1/4 of a bag of pool salt. That sounds like a sales pitch to me. Also, they said that it requires a filter change every 3-4 months that is $125.

 

[cranbiz]

Forget the built in salt system, go with a drape in unit like the Saltron Mini if you want a salt system.

 

[phonedave]

You are describing sanitization methods, not filtration systems. You filter is going to be a cartridge.

As far as Sanitization

Frog - Not my favorite. I gave it a try and did not like it. Difficult to measure using the test kit I already have for my pool, you still have a dose with chlorine from time to time, and it is pricey

Chlorine (bleach) - What I use. It works well and it takes a minimum amount of effort. I use bleach, muriatic acid, calcium hardness increaser, and Aqua Clarity. I raise my CH because I find that I get foaming from the Aqua Clarity if I do not.

SWCG - I would have bought a built in one if it was offered. I use one in my pool. Adding bleach is adding salt to your water anyway (as is sweating in your hot tub). I don't see how there is any special hot tub salt. As long as it is pure (as close as possible) NaCl (no iodine or anti caking agents) it is all the same. I will likely put a drape over unit in my tub eventually. It is just my engineering brain that does not like the idea of it as an "add on". I also need to run electric to the tub area (aside from the dedicated tub circuit) if I am going to put one in. I think I will be able to make it "nice" (to me) as opposed to screwing it to the side of the hot tub and running a cord across my patio.

 

[brent]

If you are at all like us you likely will find you use the hot tub more often than the pool. We use our hot tub all year and even in the winter doing the quick step through the snow. But using a SWG system in the pool … we have one … necessitates a shower after a swim but we are happy NOT to need to shower after a hot tub soak. I think the hot tub water is more sanitary that the shower water too.

 

[BravoRomeo]

Frog @ease works OK, depending on your expectations, but is expensive and creates some plastic waste (cartridges). I did an extensive test run with it and wrote about it on this forum. I'd only recommend it if managing daily dosing is just too much to handle or you travel a lot. I found after a couple of months, the water would get foamy / cloudy, and battling that was more work than just manual testing / dosing.

Manually dosing is the gold standard, as far as I'm concerned. Once you have it as a simple daily habit, like brushing your teeth, it's really no big deal. It's also the least expensive method using off-the-shelf products available anywhere. A hot tub requires tiny amounts of chemicals compared to a swimming pool. A squeeze dispensing bottle that can measure in 1-2 ounces makes it a piece of cake.

I installed an aftermarket SWCG in my previous tub (fully plumbed in, so completely hidden). The unit was maybe $300 plus my time to install it. Alternatively, the drape-over units are a good option requiring no plumbing or modification to the tub. Plain pickling salt from Walmart works great. It is pure sodium chloride with no additives. You don't need special "Pool Salt". PoolCalc will tell you how much you need to add to reach the PPM required by your SWCG. I never manually added bleach. I did use dichlor for the first week to bring up the CYA to 20. The Boost function on the SWCG panel took care of post-soak needs. Easy enough to test with standard Taylor kit.

Can't say I noticed being more buoyant in my salt water tub. The unit I had only required 1800 ppm salt. The water did subjectively feel more gentle, though.

 

[5tan]

The bigger Bullfrog spas (like my A7) come with 2 big coreless filters. These are very effective at filtration especially if you do a thorough filter cleaning every 2-3 weeks, meaning use a Filter Flosser to thoroughly blast contaminants off each pleat, then soak the filters in Oxyclean/Cascade Platinum overnight, then blast the detergents off using the Filter Flosser again.

In my experience, liquid pool chlorine is easiest AND cheapest. A 3.78L jug of 10.8% is $5 and lasts 3 months, so ~$20/yr in chlorine. A SWCG costs $300ish but is 24/7 automatic dosing, roughly equal to 15yrs of manually dosing pool chlorine.

For my 1643L (434gal) tub, I manually dose 150mL of pool chlorine and 30mL of liquid enzymes pre-soak, 200-300mL of pool chlorine post-soak depending on bather load (typically heavy to extremely heavy), and run the ozonator+filtration for 7 hours post-soak, with a backwash/flush cycle every 30 minutes to circulate the chlorine to ensure no dead spots. I use an clean empty jar of pasta sauce to measure the chlorine.

While the ozonator rapidly decreases FC levels, I find that my tub is basically sterilized from the post-soak chlorination, as the water stays quite clear even after many days without adding any additional chlorine since the post-soak addition, with no smell of combined chlorine/chloramines/other DBPs (disinfection byproducts) either.

I keep my pH on the low-side of the recommended range, meaning my dry acid calculations are for a pH target of 7.2. My CYA level is currently sub-20, as I had set it to 22ish upon new fill, and have had lots of splashout and top-ups since the last fill many months ago. Chlorine is scientifically more effective at lower CYA and lower pH levels, so I add just enough dichlor for the test strips to read the next block up from zero.

I add a little scoop of dry acid every month or 2 to keep the pH down. My pH is well buffered by adding 50ppm borates via a 9kg pail of BioGuard Optimizer Plus at previous full fill, about 500g for 1643L of water.

I do a full drain about once a year, only when FC consumption becomes abnormally high (rapid depletion when ozonator is disabled, via disabling filtration cycles). Rapid depletion of FC indicates biofilm accumulation inside the plumbing, inside the removable seats, and behind the seats. Before draining, I do a purge using Ahhsome gel, and thorough wipedown of shell and behind the removable seats using diluted Ahhsome gel and the blue Lysol super-strength non-disintegrating dish sponges.

All of that to say, I spend very little time and money on hot tub maintenance, my bather loads (number of people * hours of use) are rediculously high compared to most people, and I am also out of town for 1-3 weeks at a time, with no water issues despite very infrequent changing. My protocol works for me, so I consider it cheap, easy, and highly effective. I would not recommend the FROG system at all.