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We constantly recommend borax instead of soda ash, to raise pH in pools, for a number of reasons. But, if you raise the borate level high enough (>50 ppm), there are other benefits.
In pool water, borate levels of 50 ppm or higher inhibit algae, as well as slightly increasing the water's 'sparkle' and slightly decreasing eye irritation. Please understand that the effects are not dramatic: high borates do NOT mean you can skimp on chlorine! But, having a high borate level can be the difference between returning from vacation to a clear pool instead of a green one . . . IF you did the other things right. And, it can make it more likely that your pool will open clear and ammonia free next spring. Borates are also a pH buffer in a range that's especially beneficial to SWCG (Salt Water Chlorine Generator) users.
One of the best things about the effects of borates is that they don't 'expire' or get used up: once you add it, it's there till you drain. Evaporation does NOT lower borate levels. Back washing and draining are normally the only reason borate levels drop.
The cost to treat a pool with borates is fairly modest. For a 10,000 gallon pool, you'll need 10 boxes of borax, and 3 gallons of 31% muriatic acid. At current (2012) prices at Walmart (borax - ~3.50/box) and Lowes (20° Baume(31.45%) muriatic acid - ~8/gal) your cost will be about $60.
You can treat your pool with borax two different ways: slowly, with acid first, or quickly, with borax first.
*** If you have trouble with stains, or think there is ANY chance that there are metals (copper, iron, manganese) in your pool,
or if your TA and CH are high,or if you fill with well water . . . you probably should use the SLOW method, or ask us about using boric acid, instead of borax. ***
The fast method will raise the pH in your pool to around 9 temporarily. If you have iron or copper in your pool water, this can cause stains on your pool. If you have high calcium (CH), this can cloud your pool. If you already have light stains, this can darken them.
Also, before you start, you need to know a little about the two chemicals -- muriatic acid and borax -- you are working with. Muriatic acid has very irritating fumes -- read the muriatic acid handling guide BEFORE you buy the acid. And, remember: NEVER add muriatic acid to your pool if your pump is not running.
Borax is pretty non-irritating, but it has does not always dissolve rapidly. If you add it too quickly to your skimmer, it can choke the pipe and form a solid borax plug in the pipe that is VERY slow to dissolve. Do NOT do this. Do NOT add more than 2 boxes of borax to an in-ground or large above-ground pool, or more than 1 box in an Intex type pool, in any 15 minute interval.
NEVER add borax to your skimmer if the pump is not running.
Doses per 10K gallons of pool water:
+ 10 boxes or 47.5 lbs 20 Mule Team borax
+ 3 gallons of 20° Baume(31.45%) muriatic (approximate!)
+ (OR 28 lbs granular boric acid and NO muriatic acid! -- see below for links)
The slow method (for pools with high calcium, stains, or possible stains)
1. If you KNOW you have a lot of iron or copper in your pool water, postpone this process till you've removed the metals.
2. If you KNOW you have very high TA and CH levels, postpone this process till you've lowered your TA.
3. If you have some available, add 1/2 dose of HEDP before you start.
4. Add 1/3 gallon (estimate; do NOT measure!) of muriatic acid to your pool, near the point where water returns to your pool
5. Wait 20 minutes; then add 1 box of borax to your skimmer.
6. Wait 1 hour; test your pH. If the pH is ABOVE 7.6, add an ESTIMATED 2 cups of muriatic acid. If the pH is BELOW 7.0, add 1/4 box of borax.
7. Repeat steps 4 - 6 till all the borax has been added, and the pH adjusted to 7.2 - 7.6.
8. If you want to PAUSE at any point during this process, simply adjust your pH to 7.2 - 7.6, and then continue later.
The fast method (for pools with low calcium, no stains and no metal in the water)
1. Make 100% sure you have tested your pool water with a K2006, and KNOW that your TA less than 120 ppm and CH is less than 240 ppm.
2. If your pool is filled with well water, make SURE you have no iron or copper in the pool water, using the metals bucket test.
3. Turn your pump on, and keep it on for the duration.
4. Put several boxes of borax into a bucket. Break up any lumps, so all the borax is just powder. Do NOT dump the borax into one spot: if you do, a SLOW to dissolve hard lump of borax may be formed. Instead use a scoop or plastic bowl to broadcast the borax powder around your pool.
5. If any piles of borax accumulate, scatter them with a pool brush.
6. After you've added about 1/2 of the borax, put 1/2 gallon of muriatic acid in the pool, for every 3 boxes of borax you've added (so, for 11 boxes, add only 1 1/2 gallons). Add it to the pool near the location where water returns into the pool.
7. Continue adding borax to the pool till it's all in.
8. Test the pH; if it's high (purple) add 1/4 gallon of muriatic acid for every 3 boxes of borax added. Brush the pool to stir up any undissolved borax.
9. Wait 2 hours and retest the pH. Continue adding small doses of muriatic acid every 2 hours, till your pH is below 7.6.
10. Wait 24 hours, and retest the pH. Adjust as needed till the pH remains below 7.6.
Stuff You'll Need:
+ Borax: 20 Mule Team borax in 4.75 lb (76oz) boxes. (Walmart)
+ 20° Baume(31.45%) Muriatic acid: Lowes (Neither Home Depot nor Ace Hardware list plain muriatic on their websites, but they probably have it locally. Do NOT get "safer" or "foaming" muriatic acid!)
+ Testing borate levels: Sooner or later, you'll need to be able to test borate levels; the LaMotte strips are MUCH easier to read than the alternatives, and are fairly accurate. (No inexpensive drops test is available.) If they are not available from Amazon, check the test kit info page for other sources.
Lamotte Borate strips @ Amazon+ Testing hardness and alkalinity: You need to test your hardness and alkalinity levels accurately BEFORE you start. At a minimum, you need the HTH 6-way drops kit.If your TA is over 140ppm, or your CH is over 400 ppm, ASK, before you start this process. The Step by Step page explains how to lower carbonate alkalinity. There is some consensus that it is desirable to lower alkalinity below 90 ppm before beginning.
The original method proposed for adding borax to a pool attempted to strip carbonate alkalinity from the pool, by adding the acid first. However, this method is hard on liners, and potentially damaging to concrete pools.
However, there was a point to that approach: lower *carbonate* alkalinity *also* makes it harder for algae to grow. So if you have a vinyl or fiberglass pool, you can get maximum effectiveness if you first lower carbonate alkalinity, before you add borax. It's probably reasonable to take it as low as 60 ppm. Once you add the borax, your TOTAL alkalinity -- which is what testkits measure -- will be up because of borates contribution to that test result.
It is possible to use boric acid, instead of borax, to increase borate levels. This might be the best way to do it, if you have problems with metals in your pool water. However, we don't have full dosing info yet, so you'll have to add boric acid, then follow up with borax to get the pH above 7.0.
Granular Boric Acid, 5 lb @ Amazon => $22 (4.50/lb)Caution:
Granular Boric Acid, 20 lb @ Amazon => $55 (2.75/lb)
There is some evidence that drinking water with high levels of borax can reduce potency in male dogs. So, if you have breeding male dogs, who drink a LOT of water from your pool -- it's their main source of water -- then it may not be a good idea to have high levels of borax in your pool. (Probably, you should keep people from using the pool as their main source of daily fluid intake, too!)