Doing a "Bucket Test" for Metals
In a perfect world, you'd always know everything you need to know about your pool. And, you'd know when you added a pool chemical exactly what it would do.
But, this is not a perfect world, so it's often better to experiment with a little water, rather than a whole pool full. In water treatment plants that supply potable water, or treat sewage, chemical doses and other treatments are tested using "jar testing", using special large glass jars and mixers.
"Bucket tests" for pools can be done for 5 reasons:
- Metals testing. Metals stain pools. Swimming pool water can get metals in it from many sources: algaecides, corroding heaters or pool parts, well water, water delivered by trucks, and so on. The problem is, many metal treatments HIDE the metals: they are STILL in the water, but they aren't showing up. Most tests for metals can't reliably detect sequested or chelated metals. But, a metals bucket test can answer the question, "Are there still metals in my pool water? What kind?"
- Leak testing. Pools that are in use lose water for 3 reasons: evaporation, swimmer splashout, and leaks. Especially in dry climates, it's hard to tell how much water is being lost to evaporation. One form of bucket testing can answer the question: "Is it a leak, or is it evaporation?"
- Chlorine demand testing. Often when pools have problems, it's hard to tell 'how much more chlorine' it will take to fix things. In particular, this is true when a pool is all slimed up with algae or bacterially generated ammonia. A chlorine demand bucket test can answer the question, how much chlorine will it take, to clean up my pool.
- Floc testing. Many pools suffer from the big pump / little filter problem. This isn't so bad, when all is well, but when their pool is cloudy from dead algae, or precipitated calcium, or added phosphate remover, it can be very hard to clean up. And, it can be hard to tell what well help. A floc bucket test can answer the question, "Will this floc help my pool, or mess it up worse?".
- Lime softening. Calcium levels (hardness) can get too high in pools. One way to lower hardness is to drain the pool and refill with softer water. But, this not only wastes water, it can destroy liner or fiberglass pools. Lime softening is a way of removing calcium, by adding soda ash, till the calcium in your pool clouds the pool or drops out, and then can be filtered or vacuumed out.
All bucket tests start the same way: with a bucket! White 5 gallon buckets like these from Lowes or this 10-pack from Home Depot are ideal.
You can get these at Amazon, but they are expensive there, so it makes sense to buy them locally, unless you are not near a large hardware or building suppy store. Used 5 gallon white pool chemical buckets are ideal -- if they are clean, and if you have any. A white mid-size trash can will work, too. But it HAS to be clean.
Otherwise each of the 5 bucket tests has different requirements.
When testing for metals, you'll need the following:- (2) white 5 gallon buckets.
- A 1 gallon or 1/2 gallon clean milk jug or orange juice container (to measure with) OR
- A household scale accurate to within 1 lb.
- A *fresh* jug (96 oz or 1 gallon) of plain 6% household bleach.
- A box of 20 Mule Team borax.
- An OTO testkit, like the Taylor 1000 or the HTH 6-way drops kit. (Test kit info page)
- Lids or towels you can use to cover the buckets.
- A plastic or stainless steel tablespoon measure
- A plastic or stainless steel 1/4 cup measure
- A clean household long-handled stainless or plastic cooking spoon.
To carry out the test:- Use the gallon or half gallon measure to collect pool water.
- Fill the first white bucket with 4 gallons of POOL water.
(Measure by adding 4 measured gallons OR by adding 33 lbs of water to the buckets)
- Fill the second white bucket with 4 gallons of FILL water, from whatever source is used to fill the pool.
- To each bucket, add 1/2 cup of bleach & mix (~80 gal bleach /10K gal pool -- 480 ppm)
- Mix completely with the spoon
- Wait 15 minutes, and note any color change.
- To each bucket, add 1/2 cup of borax,
- Mix with the spoon till dissolved completely
- Cover with lid or towel.
- After 24 hours, inspect. Note clarity, color and sediment, if any visible
- After 24 *more* hours, inspect. Note clarity, color and sediment, if any visible
- Test both buckets for chlorine levels with OTO. You should not get a 'normal' reading, but report resultant color.
- Report results.
- Recover the buckets, and wait 3 days, and check again.
Explanation:
As best we can determine, most tests for metals available to pool owners OR pool stores do NOT reliably indicate levels of metal present, once a stain / scale metal agent has been added. These products do NOT remove metals from the water, but they do hold them in a soluble state. Eventually they break down, and re-release the metals. High chlorine tends to break down the metal agents, and high chlorine + high pH tend cause any metals released to take a non-soluble and visible form. In a clean white bucket, even small amounts of metals should form a visible precipate.
One possible complication is that the high pH will precipitate calcium carbonate, clouding the water and obscuring the result at least temporarily. This can possibly be overcome by longer settling periods.
So, what we are doing in the metals bucket test is attempting to destroy any metal control chemicals present, then releasing the metals into a visible form, and then waiting long enough for it all to settle to the bottom.
Dose ratio calc for 1/2 cup 6% bleach per 4 gallons:
0.52 lbs/cup x 0.5 => 0.26 lbs bleach
0.26 x 0.06 (bleach %) => 0.016 lbs Cl2
4 gal x 8.33 lb/gal = 33 lbs
(0.016 / 33) x 1,000,000 = ~480 ppm Cl2
