MSI – Metal and Scale Inhibitor
MSI is arguably our most dynamic product; it serves many purposes and has uses that even we continue to discover. Originally its formula was designed to quell water fouling in industrial cooling towers. It is an all-natural chelant, which means it chelates metals and minerals in solution so that fouling will not occur.
In a swimming pool, MSI is primarily used to prevent metal stains and carbonate scale from occurring. MSI is great for new pool startups–particularly plaster startups. It is applied at the rate of one quart (32 oz.) per 10,000 gallons on startup. Pour the entire startup dose into the water when there is about four (4) inches of water in the bottom of the pool. It will coat the walls as the pool fills up, and work to minimize calcium hydroxide (plaster dust) and protect the surface while it cures.
MSI is not a miracle product, but it does cover for a lot of mistakes in pool management. In reality, the best thing for water balance is following the Langelier Saturation Index (LSI). Our app is actually called LSI Calculator for a reason…it makes it easy for you dose your chemistry to stay in range of the LSI to prevent scale and etching from occurring.
Most sequest/chelant products in the pool business are phosphonic-acid based, which is basically liquid phosphates. Phosphonic acid is good for sequestering metals and preventing stains, but it has its shortcomings. Mainly, a phosphate remover like CPR will wipe out a sequestering agent.
MSI, on the other hand, has no phosphates in it and is completely compatible with phosphate removers like CPR. Remember, we’re minimalists, and none of our products conflict with each other. Conflicting products mean wasted money and adding more chemicals to the water than necessary.
Other uses for MSI
When using any type of sequest or chelant, its interaction with oxidizers like chlorine goes one of two ways:
- Chlorine oxidizes the product over time, or
- the product is immune to chlorine oxidation, and therefore wipes out chlorine until it binds to metals/minerals.
In our case, MSI wipes out chlorine when applying the purge (or startup) dose. The weekly maintenance dose will not impact chlorine levels noticeably. That said, if you have a need to lower chlorine levels in your pool, this will do it. We recommend dividing the purge dose over several treatments to avoid zeroing out chlorine levels.
A weekly dose of MSI is effective at preventing metal stains and calcium scale from occurring, assuming you began with a purge dose. Once those problems exist, it can help remove them, but it takes time for the product to break down and pull calcium or metals back into solution.
If you have scale on spillways or water features, MSI can only get to it if it’s submerged in water. So raise the water level up, or keep the feature running so it is in contact with the affected area. Note that some calcium deposits are not actually scale, such as efflorescence, calcium nodules, calcite crystals, and uneven carbonation. MSI along with good LSI balance in the water can help prevent most of these issues, but not all.