LAS & Sodium Hydroxide Storage Tanks for Water

LAS & Sodium Hydroxide Storage Tanks for Water Treatment

Municipal water treatment plants often store Liquid Ammonium Sulfate (LAS) and Sodium Hydroxide within the same facility, sometimes within the same building. Both are essential to the treatment process, but they ask almost opposite things of the tanks that hold them. Understanding those differences is key to choosing the right tank for the job. 

LAS and the chloramine connection 

Liquid Ammonium Sulfate is most often used in municipal and industrial water and wastewater treatment as a source of ammonia in chlorination. Combined with chlorine, it forms chloramines, a disinfectant that tends to hold its residual longer through a distribution system than chlorine alone. That role makes LAS a quiet but essential part of the disinfection process at many plants. 

From a storage standpoint, temperature isn’t the primary concern with LAS. What matters more is keeping the chemical in a cool, dry, well ventilated area, away from moisture and incompatible substances. Assmann recommends LAS tanks be constructed of Linear or Crosslink Polyethylene, either single or double walled, with specific accessories like proper venting, fittings, manways, and secondary containment specified to the application. Tanks are available at a 1.9 specific gravity rating for additional wall thickness and extended service life. 

Sodium Hydroxide: hot on delivery, unforgiving in the cold 

Sodium Hydroxide, also known as caustic soda or lye, presents a very different problem. It’s frequently delivered hot, which is one reason Assmann recommends Crosslink Polyethylene over conventional polyethylene for this application. Crosslink has a meaningfully higher softening point, so it can accept a hot delivery without added stress on the tank wall. 

The bigger risk shows up on the other end of the thermometer. Fifty percent Sodium Hydroxide can begin to solidify once temperatures drop into the mid-40s to mid-50s Fahrenheit range, depending on concentration. Once it crystallizes, restoring it to a usable liquid state is difficult and can disrupt plant operations for days. That’s why Assmann offers Heat Tracing and Insulation packages in 50, 80, and 100 degree Fahrenheit configurations, giving facilities a way to match protection level to their climate and delivery schedule. Assmann manufactures Sodium Hydroxide tanks up to 12,000 gallon capacity, all rated to 1.9 specific gravity. 

One manufacturing process, two very different jobs 

What ties LAS and Sodium Hydroxide storage together isn’t the chemistry, it’s the tank building process behind both. Every Assmann tank is manufactured using non-shielded molds, low temperature heat between 450 and 550 degrees Fahrenheit, and gradual air cooling rather than a water quench. That gradual cooling allows the crosslinking reaction to complete evenly through the tank wall, producing the uniform wall thickness that holds up whether a tank is managing ventilation for LAS or thermal extremes for Sodium Hydroxide. 

Both chemicals are also covered under Assmann’s NSF/ANSI 61 certification for chemical storage, the standard responsible for certifying that drinking water treatment chemicals and the components that touch them won’t introduce contaminants into the water supply. That certification requires ongoing product testing and material analysis to maintain, not a one time approval. 

Getting the accessories right matters as much as the tank itself 

A tank is only as good as the accessories built around it. For LAS, that typically means proper venting sized to prevent vacuum or pressure buildup during fill and drain cycles, along with secondary containment where the application calls for it. For Sodium Hydroxide, it means selecting the right heat trace and insulation package for your climate, not defaulting to a one size fits all solution. Under-venting and mismatched thermal protection are two of the most common causes of early tank failure, and both are avoidable with the right upfront specification. 

Working with a tank builder that understands both problems 

LAS and Sodium Hydroxide may sit on opposite ends of the storage spectrum, one built around ventilation and containment, the other around managing hot delivery and cold weather crystallization, but both deserve a tank builder who treats the specifics seriously. Assmann’s team works directly with municipal plants and their distributors to specify the right material, wall rating, venting, and thermal accessories for each application, backed by a five year warranty on every tank. 

Ready to talk through your LAS or Sodium Hydroxide storage needs? Request a quote from Assmann or explore the 

Chemical Applications library for guidance specific to your chemical.