Joe Laurino on Fill Water Problems

Pool fill water is one of the most overlooked reasons a new pool startup goes sideways. When a fresh plaster, pebble, fiberglass, or vinyl pool gets filled, whatever is in that source water becomes part of the project, including metals, tannins, and fine particulates. For pool service professionals, the risk is real: staining, discoloration, and customer complaints often show up after the surface is already exposed. The fix starts before the hose goes in. Testing fill water for inorganics and organics helps you predict problems, choose the right filtration, and avoid chasing issues with costly chemicals after the pool is full.  

A key point is that metals show up in different forms depending on the source. Municipal water is often treated with an oxidizer like chlorine, which can turn dissolved metals into extremely fine particulate iron that still comes out of the tap. Well water can deliver both particulates and dissolved metals at the same time, which is why a simple “pore size” pre-filter may not be enough. Size-based filters behave like a cartridge filter: they catch larger solids but let smaller suspended particles and dissolved metals pass through. Carbon filtration can help with organic contaminants like tannins and humic acid, and it may grab a small amount of metal, but it is not a dedicated metal-removal solution the way resin or specialized polymers can be.  

That’s where high-flow, multi-stage fill water filtration matters. A system that combines a metal-targeting polymer layer with a pleated carbon filter can address both dissolved metals and organics while still keeping the fill rate practical for protecting a new surface. The discussion also highlights stepping up filtration when the water has color or heavy organic load: adding additional carbon block stages and a final polishing filter can reduce water down from roughly 10 microns to a much finer level, even approaching sub-micron filtration. The practical takeaway is to match the filter system to the test results, not to guess, and to remember that “city water” is not always clean water, especially in regions where municipal supply is still groundwater-based.  

The episode also lays out a clear three-part pool startup process designed to protect surfaces and simplify balancing. Step one is filtering the fill water so the best possible water touches the finish first. Step two uses a startup treatment designed to address plaster dust and water balance: breaking calcium carbonate dust into calcium ions and carbonate ions can support calcium hardness and alkalinity targets while pumps and circulation are running. That same approach can include a long-lasting sequestrant to bind metals that still get introduced, plus a buffer system and a “floc to suspend” method that keeps debris from settling onto the surface while filtration clears it quickly. Step three adds ongoing metal capture in the system to reduce the chance of stains later. Whether you manage new pool startups weekly or only occasionally, building a repeatable fill water testing and filtration workflow can save hours of cleanup and protect your reputation.