Hi Kat:
It sounds like you don't have ENOUGH sanitizer if you are only using 3 tablespoons a week of dichlor ("I use about 3 tablesthingys once a week. Maybe too much?") and that's ALL you do.
N2 is made to be used with MPS (see
SpaTime products available at Lowes for an MPS source) on a DAILY basis. After using and trying to "figure" this out for awhile, here's what I've learned.
For N2 to be 100% effective, you need to use MPS DAILY. The N2 instructions say "add 1 tablespoon of MPS per 250 gallons of water BEFORE each use." N2 also says it's OK to substitute dichlor, but this kind of defeats the purpose. So, even if you DON'T use the spa, you should add the MPS a least once per day. I've noticed when I don't add MPS daily that water chemistry becomes problematic.
As mentioned, N2 says you should add MPS BEFORE each use. I think they say this because they want your use time to ALSO act as release time for the MPS oxidation process, along with oxidizing new contaminates (added while you're using the spa) at the SAME time (killing two bugs at the same time, so to speak). This strategy oxidizes stuff as quickly as possible, reducing stress on the N2 water balancing process.
N2 also recommends dichlor "if the water becomes cloudy." I should note that neither an MPS or dichlor maintenance routine is discussed in the N2 FAQ website except for this:
Q: Do I still need to use chlorine? Why?
A: Yes, you need to use a small amount of residual oxidizer. With the Nature2 system* you can reduce the clorine level to just 0.5ppm. We recommend low levels of free chlorine (0.5 PPM free chlorine minimum). You won't feel, smell or be affected by chlorine at this level.
So, what's the bottom line?
As Stuart suggested, DRAIN and start over. The product you are currently using is
PROBABLY an "enhanced shock" with a dichlor base, along with clarifiers, buffers, etc.
If it is, try this:
Refill the spa, shock using your current “enhanced shock” product at about 2 tablespoons per 250 gallons (this adds the BASE dichlor level). Run the spa with the cover off, until the smell decreases. Check pH and calcium, balance water.
Put in Nature2. Let the tub sit for 1 day with normal circulation as it comes to heat. Recheck pH and calcium. Balance if necessary. Start using the tub. Before each use, add MPS at 1 tablespoon per 250 gallons. Run the tub like you normally do. "Free Chlorine" will start to gradually decrease on your test strip. Even if you don't use the tub for a SINGLE day, add MPS. If you go SEVERAL days without use, add MPS every OTHER day. DON'T skip MPS, even if not using the tub, adding it at LEAST every 3rd day. If you lose the "routine," start over with the "enhanced shock" procedure. If you have a PLANNED event with more people, use the "enhanced shock" routine BEFORE the event, or at least AFTER, if a bunch of people come over unexpected.
On Saturdays (or another week day), REGULARLY use the "enhanced shock" routine along with cleaning the filters. Cleaning filters is easier when they are less dirty. If you notice ANY foam that can be "scooped up" and doesn’t disappear, use a clarifying agent about one hour AFTER shocking. Generally, if you are on the "program" foam should NOT be an issue.
This routine should result in roughly a .5 ppm free chlorine level on a test strip. It will vary occasionally, going from HIGH to low following shock routines. Chemistry should be good too, because the "enhanced shock" uses a "buffer" for water balance. With tub use, pH naturally goes "low," with "pH UP" (baking soda) added for adjustment. The "enhanced shock" takes care of this, but you still may need to adjust pH on occasion. Calcium should also be checked monthly.
Following this "program" N2 should work VERY well. I've used it for more than a month now with GOOD results, with "heavy" use in a 500 gallon tub. I found, however, that with "heavy use" (I define "heavy" as more than 2 people in the tub at once, at least 2 times per week, in MY case 6 to 8, with a second shift of 6 to 8 kids) a regular dichlor shock routine is a MUST. Without a dichlor shock (just MPS and MPS as a "shock"), as N2 suggests, the water had problems. Using BOTH dichlor and MPS took care of this.
Anyway, this is what worked for me. Hope it helps. Post questions if you have them...
Drewski