Issues maintaining chlorine levels

[WaseemKhaliq]

Good evening everyone,

I’m a relatively new hot tub owner, got mine at the end of September 2021.

This week I’ve been having some issues maiming my water and looking for some guidance.

Last Saturday (7days ago) I had some people coming over so Tested my water and saw that my chlorine levels were very low.. added some chlorine and let it sit upset around. When my guests arrived the level of free chortling was at about 6 (little high but all good since we were about to use it). As we were leaving i added in another tea spoon amount of chlorine into the tub, let it circulate and 20 mins later closed up the tub for the night.

Used it on Monday night solo for 20 mins

On Wednesday day I tested my water and found the chlorine back down to almost nothing and noticed that the water looked a little cloudy at is deepest level.

Added a few caps of shock and then a few hrs later added a cap of chlorine. 

Checked the water Thursday and noticed that my chlorine was still a little low and added more chlorine in the morning. Came back home in the evening and saw that my chlorine level was stupid high and my alkalinity dropped to 50.. added alka-plus and left it for the night.

Checked Friday morning and chorine was back to 3 and alk was still low at 70. Added more alk and went out for the day. Returned Friday evening and saw that my chlorine dropped to 1.3 and alk stabilized at 110. Took a dip for 20 mins and added another 10 grams or so of chlorine and called it a night.

Saturday evening after coming home from work I checked my chlorine levels and it was at 0.7.

I feel like I can’t keep the chlorine in the tub! My understanding was a cap full should last a week but at this rate I’m using 2.5-3 caps a week.. seems a little much, no?

I just added yet another full cap of chlorine Saturday evening and tested the water 30 mins later and the it was back to being crazy high at 9 ppm

I should mention that through all of this my PH has been pretty stable at 7.4-7.8.

Any thoughts??
 

[dashmer]

10 hours ago, WaseemKhaliq said:

Last Saturday (7days ago) I had some people coming over so Tested my water and saw that my chlorine levels were very low.. added some chlorine and let it sit upset around. When my guests arrived the level of free chortling was at about 6 (little high but all good since we were about to use it). As we were leaving i added in another tea spoon amount of chlorine into the tub, let it circulate and 20 mins later closed up the tub for the night.

My general take away from your post is that you are not using enough chlorine and/or MPS to meet your bather load.  Each time my wife and I use our tub, we treat it when we get out based on the length of time we are in. 

In your example above, you did not say how long you were in the tub. Lets say you were in for 30 min and there were 4 of you.  You may need as much as 14 ppm FC to clean up plus more for residual.   You added 6ppm before your dip and another 2 ppm after.

If you dig around this forum, you will find posts from chemgeek that give a rough demand of how much Cl you will need to oxidize bather waste.    Here is a quote from one of his posts:

If you weren't using an ozonator, then I could give you a rough rule-of-thumb which is that for every person-hour of soaking in a hot (104ºF) tub, it takes 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize the bather waste.  These amounts are independent of spa size.  After that, the FC level drops by around 25% every 24 hours.
 

So for chlorine, chemgeek recommends 7ppm FC for each bather hour in a hot 104 degree tub. We find that at 100 degrees, we use more like 5ppm per bather hour.  Note that this covers only the oxidization role of chlorine and you will need to have extra for the sanitation role.  So in our case, if my wife and I were in the tub for 30 min, we would add 5 ppm for oxidization (shock) and another 4 ppm for sanitation/residual.  Use the pool calculator to determine how much Cl you need for the various types and strengths of chlorine.  Dont forget that residual chlorine will decrease anywhere from 25-50% per day while the tub is not in use.

 

[RDspaguy]

Chlorine granules for spas are usually sodium dichlor, which is almost half cya. Cya over 30 starts to bind up your chlorine, making you need an ever increasing chlorine level to maintain sanitation. This is why we recommend the dichlor/bleach method.

If your spa has an ozonator (many new spas do) then it's working as it should and burning off cc and excess fc. 

We recommend ahhsome spa purge for all new spas. You have to drain it after use, so get some before you drain it. All kinds of nasty can grow in those pipes between testing at the factory and arrival at your house.