Alkaline and acid cleaners aren't interchangeable. They target different types of buildup, and a draft system that only gets one or the other is only half-cleaned. Here's what each one does and when you need both.
What Alkaline Cleaning Does
Alkaline cleaners — typically caustic-based solutions with a pH above 11 — are the workhorse of routine draft line maintenance. They break down organic deposits: proteins from beer, yeast cells, and the microbial biofilm that forms on the inner wall of beer lines between cleanings.
The chemistry is straightforward. High-pH solutions saponify (break apart) protein chains and disrupt the polysaccharide matrix that holds biofilm together. That's why the Brewers Association Draught Beer Quality Manual specifies alkaline detergent as the standard cleaner for every two-week cleaning cycle. It's the right tool for the biological contamination that accumulates in normal operation.
Alkaline cleaner needs adequate contact time — at least 15 minutes circulating through the line — at the correct concentration, typically 2–3% solution depending on the product. Too dilute and it won't fully disrupt biofilm. Too concentrated and it becomes harder to rinse completely, which can leave a residue that affects beer flavor. [INTERNAL LINK: why draft beer lines need cleaning every two weeks]
What Acid Cleaning Does
Acid cleaners — phosphoric acid or a blend of phosphoric and nitric acid, with a pH below 3 — target inorganic mineral deposits that alkaline cleaners can't touch. The main targets are beer stone and hard water scale.
Beer stone is calcium oxalate, a mineral compound that precipitates out of beer and bonds to the line wall over time. It looks like a grayish-brown film or crust inside the tubing. Alkaline cleaner will not remove it. Beer stone is acid-soluble, which means only an acid cleaner will break it down. [INTERNAL LINK: what is beer stone and why does it ruin your draft lines]
Hard water scale — calcium carbonate and magnesium deposits from tap water used during cleaning — also accumulates in lines over time and requires acid to dissolve. Philadelphia's municipal water is moderately hard, which means scale buildup is a real factor for any bar on city water.
The Recommended Alternating Schedule
The Brewers Association recommends alkaline cleaning at every two-week interval and acid cleaning quarterly — roughly every 13 weeks. Some high-volume operations or bars in hard water areas benefit from acid cleaning every 6 to 8 weeks instead.
The sequence matters. An acid cleaning done on a line with heavy biofilm won't penetrate effectively — the organic layer shields the mineral deposits underneath. The correct order is alkaline first to remove organic buildup, then acid to address mineral scale. In practice, when a quarterly acid cleaning is due, the technician performs the alkaline clean first, then follows with the acid cycle in the same visit.
Can You Use a Combined Cleaner?
Some products marketed as "dual-action" or "one-step" cleaners claim to handle both organic and mineral deposits in a single pass. These exist and some are legitimate, but their performance depends heavily on the specific chemistry of the product and the condition of the lines.
In general, a dedicated alkaline clean followed by a dedicated acid clean at the appropriate interval will outperform a combined product, particularly in lines with established beer stone buildup. The Brewers Association's guidance does not recommend combined products as a substitute for the alternating protocol.
What Happens When Acid Cleaning Gets Skipped
A system that gets regular alkaline cleanings but never gets an acid treatment will accumulate beer stone over time. Beer stone is porous. It harbors bacteria in a way that smooth line walls don't, and it provides a surface that makes future alkaline cleanings less effective. Lines with heavy beer stone buildup eventually reach a point where standard cleaning can no longer fully remediate them — at that stage, replacement is the only option.
Skipping quarterly acid treatments doesn't produce an obvious immediate problem. The deterioration is gradual. But after a year or two without acid cleaning, the line condition is meaningfully worse than one maintained on the full protocol — and the off-flavors that result are real. [INTERNAL LINK: what's that off-taste in my draft beer]
Acid Cleaning Safety
Acid cleaners are corrosive and require proper handling. The technician needs appropriate PPE — gloves, eye protection — and the lines must be thoroughly flushed after acid treatment before beer is reintroduced. Residual acid in a line will ruin a keg and can present a health hazard. This is one area where having a trained professional do the work pays for itself. An incomplete rinse after acid cleaning is one of the more common DIY mistakes.
If your draft system hasn't had an acid cleaning in the last 90 days, it's overdue. Call Philly Draft Cleaners at (267) 282-1002. We serve bars and restaurants across Philadelphia and the surrounding area.