Hot Tub question - Balancing the water

OK, its a hot tub question, but with the pool closed for the winter its the only outdoor water I can have fun in. I have a 6 person soft tub that has the following readings.

Bromine 6
PH (ranges from 7.0-7.9 from week to week, most of the time its low and i have to raise it)
Alk - 200

I currently use a bromine floater and use that all in one shock every week that says it has a ph lock/alk balancer blah blah blah. I also use Ph+ and Ph- (the cheap powder stuff from home depot) to balance the Ph.

My question is. My ph values seem to be up and down every week, is this because of the high alk? The manual says to replace 100% of the water every 3 months, so with a change of water due for me in another month do I worry about the alk if I constantly adjust the Ph? or should I really be concerned with bringing the alk down... and the second question is how do I bring it down in a hot tub? is it the same deal, lower the Ph to 6.8 and then aerate till the Ph rises to 7.6. We currently only use the hot tub once per week so its not getting used a whole ton.

thanks in advance

I suspect you are using MPS (postassium monopersulfate) as your shock. This is most common in bromine systems. It is not the best choice, IMHO, becuase it lowers pH, adds sulfates, and is expensive. You can effectively shock with bleach (you will not have chlorine, it is instantly converted to bromine) 3/4 cup of regular 5.25% or 1/2 cup of ultra 6% bleach will effectively shock 250 gallons of water in a bromine spa. Tablets contain both bromine AND chlorine so you are not adding anything that the tablets aren't! (The term 'shock' is not entirely accurate for a bromine system--oxidizer would be a better term as it's purpose is to oxidize the bromide in the water into hypobromous acid. Effective oxidizers are unstabilized chlorine, ozone, and MPS.
One final note, be sure to add sodium bromide at each refill to create the bromide reserve in the water. You can buy it in little packets or in jars. The bromide level should be around 30 ppm (no easy test for this so just follow the dosing on the package!). This step is often overlooked but it insures that you have a Bromine system from the start and sanitized water from the start. If you rely on tablets to do this it literally takes weeks for enough bromide to dissolve in the water and it is the chlorine in the tablets that you are measuring at first and that is in your water, not bromine.
Is your all in one product one that uses a phosphate buffer system or a borate buffer system? I don't like all in one products (expecially those that use phosphate buffers) since they often times complicate maintenance. Your alk is high and you are adding most likely acidic MPS with a buffer built into it. It drops your pH and then your high ALK causes it to go back up.|Also the constant airation in a spa can cause the pH to rise.

You lower the ALK in a tub exactly as you do in a pool! In fact it's easier to aerate since you just have to turn on the bubblers and open the air valves on the jets and you will find your pH will rise in a very short time!
Stay away from the pH increaser! It is sodium carbonate and will raise your ALK along with your pH! Use Borax to raise the pH and you won't have the problem with your ALk going through the roof!

On next fill try balancing your water with just baking soda if your alk is below about 150 ppm or dry acid if it is above. (I personally kept my portable spa at about 120 when using bromine since the tabs are slighly acidic and therefore deplete pH and ALK.) Remeber to add the sodium bromide on filling (can't stress this enough!), shock with bleach initially and weekly, use your floater to maintain a bromine reading about 6 ppm, and maintain your ALK with baking soda and adjust pH with dry acid and borax and see if things don't go better. If you want to buffer the water even more add borax to 30-50 ppm and bring the pH in line with dry acid. (only has to be done on each refill and once you figure out how much you need it's pretty easy to do. You can order borate test strips online to help you the first few times--check out the thread in the 'China Shop' section of the forum called "The Great Tetraborate Experiment"--It is just as applicable to spas as it is to pools. (In fact Proteam makes a borate product spcifically for spas which is nothing more than a mix of sodium tetraborate and dry acid!)
Just my 2 cents!

Wow, that more more than 2¢... more like $20 worth. Thanks for the in depth answer. On start up I put in the 2 part A liquid/B powder to bring my bromine reserve up at initial fill. Ok to sum up the rest, sorry if I get things wrong, its been 6 months since I touched pool chemicals. I can shock with Bleach. Use borax to bring my Ph up when needed and dry acid to bring it down. where do I buy dry acid anyways, is it available at my local hardware store?? and how does baking soda fit into it? Yikes, this is what happens when you dont have your pool open all year around, you forget!

Now I just have to wait for some warm weather to drain my hot tub :-(

Quote:

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Originally Posted by CanuckPool

Wow, that more more than 2¢... more like $20 worth. Thanks for the in depth answer. On start up I put in the 2 part A liquid/B powder to bring my bromine reserve up at initial fill. Ok to sum up the rest, sorry if I get things wrong, its been 6 months since I touched pool chemicals. I can shock with Bleach. Use borax to bring my Ph up when needed and dry acid to bring it down. where do I buy dry acid anyways, is it available at my local hardware store?
You already have it...It is the pH-...look on the ingredients and you will find it is sodium bisulfate.
? and how does baking soda fit into it?
baking soda is sodium bicarbonate. You can buy it for a lot of money packaged as total alkalinity increaser at the pool store or just go to the grocery store and buy a box of baking soda. It's exactly the SAME chemical! (Some of the pool store products might say Sodium Hydrogen Carbonate instead of Sodium Bicarbonate but it's just a different name for the same chemical!) It's purpose is to raise total alkalinity! (NOt a good idea to use it to raise pH, btw, even thought it will slightly. Some people try to use it for this pupose in their spas, however)
Yikes, this is what happens when you dont have your pool open all year around, you forget!

Now I just have to wait for some warm weather to drain my hot tub :-(

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Does this raise the ante to $30;)
Still just my 2 cents!

CannuckPool, let me remind you of the thread we shared in Oct http://www.poolforum.com/pf2/showthread.php?t=6138 , I'm sorry I didn't think to tell you of the other 'chemically equivalent' items you could be using.

Sweet jesus!! I knew this topic sounded familiar! thanks again... I see your $30 and raise you $10.

Evan, I may not have said it correctly in the other post but, your 'pennies' are made of gold!