Chemicals for hot tubs

[01344neil]

Hi

Can anyone please tell me some alternatives to the really expensive chemicals sold by the hot tub chemicals.

I'd like to use Soda Crystals (Sodium Bicarbonate) as an alternative to Total Alkalinity increaser. From what I've read here, I think that's OK.

Is there an alternative to the Anti Foam on sale?

What do people use to clean their filters which is not the oh so expensive Filter Cleaner on offer?

And for anti-scale?

Thanks for your help

[PoolDoc]

Wow. Questions from somebody outside N. America, that we can actually answer. (Often, we get asked questions that require that we know what's available in your market . . . and we don't -- we just know it's NOT what we have here.)

Anyhow:

1. Sodium bicarbonate IS "Total Alkalinity Increaser", aka "sodium acid carbonate" aka "sodium hydrogen carbonate".

2. The solution to foam is to sanitize sufficiently, and drain and refill frequently. In general, if your spa is foamy and you've maintained adequate continuous halogen (chlorine or bromine) levels, you need to replace the water. (Many people in the pool industry won't get in a foamy spa!) Chlorine + filtration will NOT remove everything that spa users bodies add to the water.

3. Trisodium phosphate - Na3PO4 -- CAS# 7601-54-9. In the US, it's often sold in hardware and home repair supply stores as a cleaner. I don't know if it's available that way in the UK. Directions here: http://www.poolforum.com/pf2/showthread.php?18044

4. Anti-scale - again, regular drain and replace will usually solve the problem. I don't know about water supplies in the UK; well water from karst areas in the UK would tend to be high in calcium, but surface waters usually are not.

Assuming you have a fiberglass or plastic spa and that stainless steel or bronze are the only metals exposed to the water, THEN
=> never add calcium
=> only use alkalinity if your pH is unstable. If you can, replace baking soda with borax (sodium tetraborate, sold in the detergent section in US stores) + whatever acid you have, to buffer your pH levels.
=> if your spa is not exposed constantly to sunlight, use household bleach to chlorinate. If it is exposed, use bleach + dichlor powder or granules.

[01344neil]

Thanks very much.

Someone told me that the foam is largely from laundry detergent that comes out of people's swimming costumes so I wasn't too worried about it at this stage. My brother in law adds a liquid that just eliminates the foam but as you say it obviously can't remove the substance.

Water in the South of England is generally hard and scales up kettles, washing machines etc so I can see that it would affect the heating element of the hot tub.

I would expect the sodium bicarbonate to solve that though.

Thanks for your help.

[PoolDoc]

Nope. Adding sodium bicarb INCREASES the tendency of water to scale. There are various 'saturation' indices that give you some idea whether the water is likely to deposit calcium carbonate (often, the primary component of scale); these indices mathematically combine values for pH + temp + calcium + carbonates (alkalinity). Positive values tend to scale; negative values tend to dissolve calcium carbonate. In all of these indices, the index value INCREASES as any one component value increases.

Bicarb is added to pool and spa waters for 2 reasons: to 'balance' the saturation index, and to stabilize (buffer) the pH. For complex reasons, it does NOT work well for this purpose in heavily aerated spas ( this page explains http://www.poolsolutions.com/gd/lowe...p-by-step.html ).

If you can find it, borax would work better for you. It can help you adjust (raise) pH, buffer pH, and will not be aerated away like carbonates are. Even if not, I would recommend NOT adding bicarb to your pool, unless you have a concrete spa, have accurate test results for pH + temp + hardness + alkalinity, have calculated your S.I., and know you have aggressive water.

[chem geek]

Having the Calcium Hardness (CH) at 120-150 ppm can help reduce the amount of foaming (harder water foams less). The least expensive way to maintain the spa is the Dichlor-then-bleach method where you use Dichlor initially to build up a 30-40 ppm Cyanuric Acid (CYA) level and then switch to using bleach (using Dichlor once a month to make up for CYA loss). You need to get your Total Alkalinity (TA) down to around 50 ppm and use 50 ppm borates (say, from adding boric acid) as this will reduce the rate of pH rise. However, with chlorine, you need to add it to the tub every day or two. If you soak every day or two, that's no problem and you dose after each soak. If you only use the tub infrequently or just on weekends, then using bromine may be a better choice for you.