Cloudy, Foamy, Green or Smelly? How to Tell Which Hot Tub Water Problem You Have: Questions Answered

Hot Tub Care
Tub and Pool Answers Team

Cloudy water, persistent foam, a green tint, or an odd smell—these four common symptoms all signal water trouble, but each stems from a distinct cause requiring a different solution. This hub helps you pinpoint which problem you’re facing so you can target the right fix, not just apply general advice.

Why is my hot tub water cloudy even after I’ve added chemicals?

Cloudiness often points to a clogged filter or high pH rather than a simple lack of sanitiser. High pH or poor filtration can prevent the water from clearing effectively. Check your filter flow and pH balance first. Full details are in our guide to Lay-Z-Spa Cloudy Water: Why It Keeps Coming Back (and the Order to Fix It) .

Why does my inflatable hot tub keep foaming after every use?

Foam is commonly caused by surfactants, such as detergent residue left on swimwear. The jets agitate these substances into bubbles. Full details are in our guide to Why Is My Inflatable Hot Tub Foamy? The Usual Causes, in the Order to Check Them .

My hot tub water turned green overnight – should I drain it?

Green water is typically an algae bloom, which occurs when sanitiser levels drop too low. The decision to treat or drain depends on the severity of the bloom and your usage patterns. Full details are in our guide to Green Water in an Inflatable Hot Tub: Treat It or Drain It? .

Why does my hot tub smell like chlorine even though I just shocked it?

A strong chlorine smell often indicates combined chloramines. These form when chlorine reacts with contaminants like sweat, rendering it less effective. This signals the need for oxidation, not more chlorine. Full details are in our guide to Why Does My Hot Tub Smell? Musty, Fishy and Chlorine Smells Explained .

Why is my hot tub water milky straight after shocking?

Shocking oxidises organic matter, breaking it into smaller particles. The temporary cloudiness you see is the byproduct of this process, which should clear with filtration. Full details are in our guide to Milky Hot Tub Water Straight After Shocking: Normal or a Problem? .

Why does the scum line at the waterline keep coming back?

Scum lines are caused by body oils and lotions that float on the surface and cling to the tub’s edge, bypassing the filter. Wiping it away is temporary; you need to reduce the source of the oils. Full details are in our guide to Scum Line and Bubbles That Won’t Go: Biofilm, Lotions or the Filter? .

Why is my hot tub water cloudy after I changed the filter?

A clogged cartridge filter in an inflatable spa like a Lay-Z-Spa can restrict water flow, allowing fine particles to recirculate. Check if the new filter is installed correctly or if it’s already blocked. Full details are in our guide to Lay-Z-Spa Cloudy Water: Why It Keeps Coming Back (and the Order to Fix It) .

Why does my hot tub smell musty or earthy?

A musty smell often stems from biofilm in the plumbing or stagnant water, a biological issue sanitiser can’t always reach. This requires a biofilm treatment approach. Full details are in our guide to Why Does My Hot Tub Smell? Musty, Fishy and Chlorine Smells Explained .

Why is there foam on the surface but the water looks clear in a glass?

Surface foam is a tell-tale sign of surfactants, even in otherwise clear water. The foam will likely return until the source, like detergent residue, is removed. Full details are in our guide to Why Is My Inflatable Hot Tub Foamy? The Usual Causes, in the Order to Check Them .

Why is my hot tub water green even though I use chlorine?

Green water indicates algae, which can take hold if sanitiser levels drop during periods of non-use or if the pH is too high for the chlorine to work effectively. Full details are in our guide to Green Water in an Inflatable Hot Tub: Treat It or Drain It? .

Why does my hot tub smell fishy?

A fishy odour suggests organic matter is decomposing because the sanitiser has been overwhelmed. This needs shock treatment and improved circulation. Full details are in our guide to Why Does My Hot Tub Smell? Musty, Fishy and Chlorine Smells Explained .

Why won’t the bubbles in my hot tub go away?

Persistent bubbles are a classic symptom of surfactants. Anti-foam is a temporary fix; the long-term solution is to eliminate the source of the contamination. Full details are in our guide to Why Is My Inflatable Hot Tub Foamy? The Usual Causes, in the Order to Check Them .

Why is my hot tub water cloudy after a party?

Cloudiness after heavy use is commonly due to a build-up of bather waste like sweat and sunscreen. Check both the filter and the pH balance, as the chemistry is likely disrupted. Full details are in our guide to Lay-Z-Spa Cloudy Water: Why It Keeps Coming Back (and the Order to Fix It) .

Detailed guides:

Cloudy water and foam are the two symptoms that most frequently appear together. If you’re dealing with more than one issue at a time, it’s best to start with our triage guide rather than diving straight into a symptom-specific article.