Why do I keep getting black spots on inside cover?

[squale]

I have a Sundance Altamar spa, 375 gallons, and it's inside my garage.  

I just did a water change about 2 weeks ago.  Totally cleaned the spa with bleach and everything.  Filled it up, took a couple days to balance the water since my tap water is high in Alk and PH.

I use Dichlor once a day or every other day, about 2 teaspoons at a time, after I get out of the hottub and then if I don't go in the hottub for a couple days I will put it in like every other day.  I shock with MPS once a week.

I keep getting these black spots all over the inside of my cover.  I would assume it's black mold spots.  Also my water seems to have a weird smell to it.. not like a dirty smell.. more of a slight chemical smell I would call it.. just something I really never had before.

the only thing I have changed over the last couple of refills was that the first time I had an N2 cartridge in the tub and also used Dichlor just like I explained above.  These last couple water changes where I have been getting these black mold spots on the cover I have NOT been using the N2 cartridge... JUST dichlor and MPS.  I read online that you really don't need the N2 cartridge if you are still using Dichlor so that's why I stopped using the cartridge.

Anyhow.. I am really getting frustrated and can't figure out what is going on.  Every week or so i have to take diluted bleach and wipe down the inside of my cover to get all the black spots off of it.

any advice would be GREATLY appreciated!

[Chas]

Normally, it is a good idea to leave the lid open when you add dichlor or MPS. But in your case, you may want to try a chlorine shock with the lid down. This is not good for the cover on an ongoing basis, but it should help you get rid of the mold/algae.

 8-)

[squale]

I just read that when the PH is high the sanitizing effects of chlorine are highly reduced... and when I fill my spa with new water from the tap... my PH is at like 8.7 coming out of the tap so it takes me about a good week with ph decreaser to get the PH down into the correct range.  So maybe during this first week or two I am not adding enough dichlor to compensate for the higher PH?  Maybe I should double the amount of Dichlor I normally use in the first couple weeks until I get the PH and Alk down into the correct ranges?

[hottubdan]

What is your TA out of the tap?  Why aren't you more aggressive knocking it down?

[squale]

I'm about 210 TA out of the tap... I try to knock it down to good levels in a few days... I just don't want to put more than 3 ounces of PH Decreaser in per day..

[Chas]

In cases such as yours, I tell customers to go to four ounces at a time - and not retest sooner than four hours after putting it in.

So, if you have too, you can put in four ounces six times in 24 hours or a total of 24 ounces in one day, not allowing for sleep....

In my Grandee, I put in just shy of six ounces to start - I'm a professional - and it is good almost every time.

 8-)

[squale]

chas, since you have high ph and alk from tap water, do you notice that dichlor doesn't work as good as a sanitizer when your Ph and alk levels are high?  I think this is probably my issue.. I'm running a PH of around 8.2 for the first few days and my alk is around 200.  So when I put my normal dosing of Dichlor in every day (2 teaspoons) maybe that is NOT enough sanitizing effect because the PH is too high and renders the sanitizing effects of dichlor almost useless???  they say at high PH levels the oxidation effect of Dichlor is still good, it's just the sanitizing effect goes away..

[Chas]

I don't let my TA and pH get or stay high. I lower it as I'm filling, and continue to work on it so that within hours of a fresh fill I have balance water. Then I shock with Chlorine, and I'm off and running.

Yes, high pH can lock the chlorine, and low pH gives it super potency.

Your issue may be the times in between uses or in between does of chlorine. If you skip several days of use, go ahead and toss in some Dichlor anyway.

If you want to go to a floating feeder system, which is good for people who have mold, black algae or other issue revolving around low use, this is the only one which will not kill shells, pillows and covers -



 8-)

[squale]

I thought you can't float dichlor because it dissolves too fast?  and regular chlorine tablets like you use in the pool are very low in PH and also you need to mix it with another agent or something right?

[hottubdan]

Chas is recommending a chlorine-free bromine system.

Still recommending you know your TA and pH down day of fill up.  Yours is a unique situation.  There is nothing magic about how much pH decreaser you can add in a day.  

[tanstaafl2]

 Every week or so i have to take diluted bleach and wipe down the inside of my cover to get all the black spots off of it.

What concentration of diluted bleach do you use to clean the cover? I am an infrequent user and use only dichlor, both after a soak and as a shock. But occasionally I get those black spots on the underside of the cover and they can be tough to clean with standard cleaners and I don't really want to get the cleaning agent in the tub anyway.

10 to 1?

[squale]

prob more like 5:1 bleach to water..