Glycol Water Tank （GWT）& Cold Water Tank(CWT)

What exactly is the difference between the Glycol Water Tank (GWT)& Cold Water Tank (CWT)? How do we make choices as a brewer?

Cold liquor tanks. Cold water does not contain alcohol. This means that the temperature of the liquid in the tank is maintained above freezing. Set the temperature according to the brewing process requirements. The main sources of these water are tap water, ro water, etc. that can be used for brewing.

Glycol water tank.The biggest difference between the GWT and the CWT is the liquid inside. The main component is a mixture of tap water and ethanol or propylene glycol, which is expensive. The function of alcohols is to lower the freezing point, so that the working temperature of the glycol is generally maintained at about minus three degrees to minus five degrees.It cannot be in direct contact with wort, and cannot be used for brewing. It can only be circulated in the glycol tank and pipeline.

Both can be used as cooling tanks, during design the brewery, you could decide whether to use it or not after full consideration according to the project budget, room space and brewing process design.

In order to avoid the burden on the cooling system due to excessive heat exchange power in the process of cooling the wort at the plate heat exchanger, which will affect the fermentation temperature control, CWT can be used as a buffer tank to receive the heat and keep the glycol tank running at lower temperature.

To sum up

1. The rational use of CWT can save water and energy consumption, reduce hot water preparation time, increase brewing batches, and ensure that the cooling of the fermentation process is not affected. Commonly found in brewing systems above 10hl or brewing several batches per day.
2. For smaller breweries or brewpub We can eliminate the cold water tank and only use the glycol tank to cool both the plate heating exchanger in brewhouse and the fermentation tank. When cooling the hot boiled wort, it will cause the glycol water to heat up rapidly. But if you have budget and space limit. Or you’re only to brew one batch of beer in one day. You can just use glycol tank do all the cooling work. Therefore, it is usually find in brewpub or restaurant.

Frequently Asked Questions (FAQ)

1) What mixture should I use in a Glycol Water Tank (GWT) for brewery cooling?

• Food-grade propylene glycol (PG) mixed with deionized/RO water. Typical setpoints: −3 to −5°C with 25–35% PG by volume; go to 35–40% PG if you need −8 to −10°C for crash or slush-prone lines.

2) How is a Cold Water Tank (CWT) different operationally from a GWT?

• CWT stores potable cold liquor (no alcohol) used on the wort side of a plate heat exchanger (PHE) and for utility needs; GWT circulates closed-loop PG/water to jacketed vessels and NEVER contacts wort or product.

3) When can I eliminate the CWT and cool directly with glycol?

• In small brewpubs running one batch/day and modest crash demands, you can skip a CWT. Expect larger instantaneous heat load on the chiller and temporary glycol temperature rise during knockout—plan capacity accordingly.

4) What tank sizing rules of thumb apply to GWT & CWT?

• GWT volume: 1.0–1.5× total glycol in piping + jackets, plus 10–20% expansion headspace.
• CWT volume: at least 1.0–1.5× a single knockout water demand so you can chill and reuse hot water efficiently.

5) How do I protect my GWT system from corrosion and biofilm?

• Use RO/deionized makeup water, maintain PG concentration and inhibitor package per vendor, keep a sealed vented lid, add side‑stream filtration (50–100 μm), and test pH (target 8–10 for most inhibited PG fluids).

2025 Industry Trends for Glycol Water Tank (GWT) & Cold Water Tank (CWT)

• Higher-efficiency chillers and variable-speed pumps: VFDs on glycol pumps with DP setpoint control reduce energy and cavitation.
• DAW integration: Breweries add small deaerated water loops that pre-chill CWT water, improving knockout and reducing oxygen pickup risk.
• Heat recovery normalization: Knockout heat captured to pre-warm HLT; breweries target plant water-to-beer ratios near 3.0–3.8:1.
• Smarter controls: IO‑Link/Modbus sensors log tank temps, glycol concentration via refractometers, and trigger alarms for low flow or low concentration.
• Environmental focus: Propylene glycol remains preferred (food grade, low toxicity) with documented disposal and spill SOPs to meet local regulations.

Cooling Performance & Utilities Benchmarks (2024–2025)

Metric	Typical Range	2025 Best Practice	Impact	Source/Notes
GWT setpoint	−3 to −5°C	−4°C with 30–35% PG	Stable crash cooling	Vendor/MBAA
PG concentration	25–35%	30–35% (brewpub); 35–40% (colder setpoints)	Freeze protection, pumpability	PG supplier data
CWT temp	2–6°C	2–4°C with pre‑chill/heat recovery	Faster knockout	Brewers Association
Water-to-beer ratio	4.0–5.5:1	3.0–3.8:1 w/ heat recovery	Utilities saved	BA sustainability
Pump control	Constant speed	VFD with DP control 10–20 psi	Energy, cavitation reduction	DOE/MBAA
Glycol testing	Annual	Quarterly refractometer + inhibitor check	Reliability, corrosion	Vendor guidance

Authoritative sources:

• Brewers Association (sustainability, cellar utilities): https://www.brewersassociation.org/
• MBAA Technical Quarterly (cooling, heat recovery, PHE design): https://www.mbaa.com/
• ASHRAE guidelines for process cooling best practices: https://www.ashrae.org/
• Propylene glycol technical data (food-grade): major suppliers such as Dow/ADM (product bulletins)

Latest Research Cases

Case Study 1: Adding a CWT Buffer Stabilizes Fermentation Cooling (2025)
Background: A 10 hL brewpub ran knockout directly on the glycol loop; tank crashes during busy weekends were slow due to glycol temperature spikes.
Solution: Installed a 1,000 L CWT fed by the chiller during off-peak hours; re-plumbed knockout to use CWT first, with glycol as secondary only when needed; added VFD on glycol pump and differential-pressure control.
Results: Knockout time improved by 18%; glycol temp spikes dropped from +4°C to +1°C; fermentation jacket stability improved, reducing diacetyl rest overruns and shortening average tank turns by ~0.5 day.

Case Study 2: PG Optimization Cuts Energy and Maintenance (2024)
Background: A 20 hL system experienced frequent pump seal wear and microfouling in the GWT loop.
Solution: Switched to inhibited food-grade PG at 33%, added side-stream filtration and quarterly refractometer checks, sealed tank headspace, and balanced loop with circuit setters.
Results: Glycol pump energy −12% after VFD tuning; seal failures eliminated over 9 months; jacket delta‑T increased by 1.1°C improving crash performance without lowering setpoint.

Expert Opinions

• Mary Pellettieri, Quality Consultant; author of “Quality Management for Craft Beer”
  “Treat the CWT as a quality tool, not just utilities—stable knockout temperatures protect flavor and reduce oxygen pickup downstream.”
• Dr. Tom Shellhammer, Professor of Fermentation Science, Oregon State University
  “Temperature stability from well‑designed GWT loops directly influences yeast performance and aroma retention—especially in hop‑forward beers.”
• John Blichmann, Founder, Blichmann Engineering
  “Right‑size and future‑proof: include tri‑clamp ports for sensors, VFD‑ready pumps, and service valves so you can add heat recovery, DAW, or extra jackets without downtime.”

Practical Tools/Resources

• BA Sustainability Benchmarking Tools (water/energy): https://www.brewersassociation.org/
• MBAA resources on PHE sizing, knockout, and glycol best practices: https://www.mbaa.com/
• ASHRAE handbooks for process cooling design: https://www.ashrae.org/
• Glycol concentration calculators and refractometer charts (supplier technical bulletins: Dow/ADM/Lyondell)
• Brewfather/Brewers Friend for logging knockout temps and utility KPIs: https://brewfather.app/ | https://www.brewersfriend.com/

Last updated: 2025-08-29
Changelog: Added 5 FAQs comparing GWT vs CWT operations, 2025 trends with KPI table, two case studies on CWT buffering and glycol optimization, expert viewpoints, and practical resources.
Next review date & triggers: 2026-02-28 or earlier if BA/MBAA release updated cooling/heat‑recovery guidance, ASHRAE updates process-cooling recommendations, or new compact DAW/CWT integration kits become widely available.