Why Is My Cask Ale Cloudy? Common Causes & Fixes

Last updated: 29 June 2026

Most licensees blame the brewery when a cask of ale pulls cloudy — but the truth is that nine times out of ten, the problem is sitting in your cellar, not in the cask. A hazy pint isn’t just a cosmetic issue; it’s a sign that your cellar temperature, line pressure, or cask handling is off, and that means you’re either pouring it away or losing money on customer complaints and re-pours. This article walks you through the real causes of cloudy cask ale, what you can actually fix yourself, and what to do when it genuinely is the beer’s fault.

Cellar Temperature Is the Main Culprit

Cask ale needs to sit between 12–13°C to pour clear and bright. Every degree above that destabilises the proteins in the beer, causes them to aggregate, and you get haze. Most pubs I know run their cellars at 14–15°C because they think that’s “warm enough” or they’ve never actually checked the thermometer. It isn’t warm enough — it’s too warm.

The frustrating part is that temperature creep happens quietly. A faulty thermostat, a door left open for stock rotation, or even the ambient temperature rising in summer will nudge your cellar up by half a degree, and within a week you’ll start seeing cloudiness in the ales. Then you call the brewery, they send someone out, they find nothing wrong with the beer, and you’re left looking like you don’t know what you’re doing.

I spent two years at my own pub wondering why my Timothy Taylor was intermittently cloudy until I invested in a proper thermometer and a log book. Turned out my cellar was running at 14.5°C in the afternoons because I was leaving the door open during service. Dropped it to 12.5°C, stopped the door-opening habit, and the cloudiness stopped entirely. No phone call to the brewery. No wasted beer. Just better pints.

The fix is simple: Install a thermometer you can actually read (not a dial one hidden behind the kegs), check it daily, and keep a written log. If it creeps above 13°C, your refrigeration unit is struggling or the ambient temperature of the room needs controlling. In summer, many pubs need to run a dedicated cellar fan or upgrade their cooling capacity.

Poor Line Cleaning and Build-Up

Bad line cleaning is the second-biggest cause of cloudy cask ale, and it’s entirely your responsibility. Every pint that flows through a line leaves behind protein residue, yeast particles, and beer stone (the crusty calcium buildup you see inside uncleaned lines). Over time, this builds up and taints the beer, making it hazy or off-tasting — or both.

Most pubs I know clean their lines once a month or when they “remember to.” That is not enough. The most effective approach to maintaining clear cask beer is a weekly line clean with a proper caustic cleaner and a soak cycle of at least four hours. I use Chemsan or a branded draught line cleaner, mix it to the right strength (read the label — do not guess), and run it through all ale lines every Sunday night when service is closed.

Here’s a detail most licensees miss: the nozzle where the beer comes out is where the most visible sediment accumulates, but the hidden problem is inside the line itself. Sediment builds up in the tube, especially in the bends, and when you pull hard on a pint (to speed things up during busy service), you dislodge it and it ends up in the glass. Customers see haze, think the beer is off, and you lose the sale or pour it away.

At my pub, I also keep a simple checklist pinned to the cellar wall: date, line cleaned, initials, and notes. It takes thirty seconds to fill in and makes sure no one “forgets” which lines were cleaned and which weren’t. Over a year, this log also shows me which lines are prone to build-up faster — usually the busiest ones — and I can clean those more frequently.

Cask Handling and Sediment Disturbance

Every cask of ale has some sediment at the bottom — it’s natural and part of the brewing process. The sediment starts to settle within 24 hours of the cask arriving at your pub, and if you leave it alone, you won’t see it in the glass. But if you move the cask, tilt it, roll it, or tap it on the side (which I’ve seen more than once), you kick up all that sediment and it clouds the beer for the next 48 hours.

This is especially common when you’re rotating stock or moving kegs around during a cellar tidy. The faster you move the cask, the more sediment you disturb. I’ve also seen bar staff accidentally kick casks with their feet or deliverymen throw them onto the gantry — both will cloud your ale for days.

Cask ale requires gentle handling because sediment disturbance clouds the product for 24–48 hours after movement, making it unpourable without waste. The solution is simple: handle casks as little as possible once they’re in the cellar. Mark them clearly so staff know not to move them. If you absolutely have to move a cask, do it slowly, keep it level, and then leave it untouched for at least 24 hours before you tap it.

Also, make sure your cask rack or gantry is stable and not wobbling. A wobbly rack will vibrate every time you’re pulling pints in a busy service, and by the end of the night, the sediment is back in suspension.

CO2 Pressure and Over-Carbonation

This one catches people by surprise. Cask ale should not be under gas pressure — it’s a naturally carbonated product. But if your regulator is faulty or someone has accidentally turned up the CO2 pressure on the line, you’ll over-carbonate the ale, and that can cause cloudiness or a soapy, over-foamy head that looks off.

Some pubs run CO2 on all lines — draught lagers and stouts need it — but ale lines should not be under pressure, or only under very light pressure (less than half a bar) if you’re using a breather valve to keep air out as the cask empties. If your ale is coming out overly foamy and cloudy at the same time, check your regulator and the pressure gauge. Many pubs have never looked at this and don’t realise they’re sitting at 1–2 bar on every line.

The fix is to ring your gas supplier or a qualified engineer and ask them to check your regulator settings. Most will do this for free. Ale lines should be at zero or very close to it. Once that’s correct, the cloudiness from over-carbonation will clear within a few pints.

When It Actually Is the Brewery’s Fault

Once you’ve ruled out the above — consistent cellar temperature, clean lines, gentle cask handling, correct pressure — there are genuine instances where the beer is faulty and that is the brewery’s responsibility. These are rare, but they do happen.

A cask that was contaminated at the brewery, or one that sat in a warm warehouse before delivery, or one where the natural carbonation process went wrong, will pull cloudy no matter what you do in your cellar. The beer will also often taste off — vinegary, or sour, or oxidised. If you pull a pint, check the taste, find it’s genuinely bad, and you’ve already ruled out your cellar, then ring the brewery and ask them to collect it.

But be honest with yourself first. The brewery will ask you: What is your cellar temperature? When was your last line clean? How long has the cask been resting? If you can’t answer these questions with confidence, they’ll assume (correctly) that the problem is your cellar management, not their beer. And that conversation is a waste of everyone’s time.

At my pub, I’ve had to call the brewery maybe three times in 15 years for a genuinely faulty cask. Everything else was on me.

Quick Fixes You Can Do Today

If you’ve got a cloudy cask sitting in your cellar right now, here’s the fastest way to diagnose and fix it:

• Check the thermometer. If it reads above 13°C, lower the temperature and wait 48 hours. Half your cloudiness problem is solved by temperature alone.
• Pull a line clean. Use a caustic cleaner, run it through the line, let it soak for four hours, then flush with fresh water. Pull a pint and see if it clears. If it does, schedule weekly line cleans from now on.
• Leave the cask alone. If you’ve been moving it, stop. Mark it with a sticker saying “Do Not Move” and give it 48 hours to settle. Pull a test pint and see if it clears.
• Check the CO2 regulator. Look at the pressure gauge. If it reads higher than 0.5 bar on an ale line, ask your gas supplier to adjust it.
• Taste the beer. If it tastes fine, the cloudiness is cosmetic and will pass. If it tastes sour or off, the cask is faulty — contact the brewery.

Most pub operators lose money on cloudy ale without realising it. A 1% stock loss on wet sales quietly costs a typical pub £3,000–£5,000 a year, and cloudiness is one of the silent culprits — you don’t always waste the full cask, but you pour away pints, give away re-pours, or sell a substandard product that damages your reputation. A proper weekly cellar check catches cask issues before they become wastage.

The best investment I made was building a simple counting routine around cellar temperature logs, line clean records, and a weekly dip of every cask. I built it on paper at first, then moved to StockTap pub stock app to centralise the records and run the numbers against my till data every Sunday. Within a fortnight, my variance went from guesswork to a number I could trust. And cloudiness stopped being a mystery — it became something I could predict and prevent.

For more information, visit SmartPubTools.