How Does A Closed Loop Recirculation System Work?


Todde Philips

🇺🇸 Retired veteran, father, rock-climbing expert & rosin connoisseur.

As the name suggests, a closed loop recirculation system is a configuration that lets hash makers recirculate and thereby reuse water during the Ice Water Extraction process of collecting loose resin, or bubble hash. The traditional approach to Ice Water Extraction does not involve recirculating water through the system, rather extractors dispose of the drainage water after it’s mixed with starting material and passes through the sieving bags. Then hash makers reintroduce fresh water into the system, where it’s used once for agitation and filtration, then drained as waste. 

In Closed Loop Recirculation, water isn’t drained as waste after one run of agitation and filtration, but rather pumped back into the agitation vessel where it can be reused for subsequent “pulls”, or batches of loose hash collection. Water stays in a closed loop (except for the first one to three washes, which are drained just like traditional set ups), and remains in continuous use. 

Since the first one to three washes or agitations of the ice water and starting material contain the most contamination, these batches of water are drained as waste after being sieved through the 25u wash bag. More on that later. 

Advantages of Using a Closed Loop Recirculation Setup for Washing Bubble Hash

There are several advantages to a Closed Loop Recirculation setup in Ice Water Extraction. Here are a few:

  • Less wasted water 
  • Less energy needed to chill water before it’s introduced into the system 
  • Lower daily operating costs  
  • Reduced time spent refilling the agitation tank with fresh water 
  • Reduced time spent collecting loose resin (more on that later) 
  • Reduced time spent adding ice 
  • Minimizes damage to the trichome heads during agitation 
  • More room for starting material in the agitation tank because less ice is needed


Read more in our article Top 5 Key Benefits from Cold Water Recirculation for Ice Water Extraction.


What Equipment Do You Need for Closed Loop Recirculation?

In addition to all the standard equipment that hash makers use for Ice Water extraction, including a mixing vessel and sieving bags, a recirculation vessel, chugger pump, and food safe hoses are key components for the set up. 


How Do You Configure a Closed Loop Recirculation System?

In a closed loop system, water runs continuously from the wash vessel, then into the collection vessel, and finally down into the recirculating vessel where it’s filtered through a 25u bag before moving back into the wash. 

It’s important to use a 220u work bag inside the wash vessel to help keep the larger contaminants out of the recirculating water cleaner and your collection bags. 

Using a 25u sieving bag inside the recirculating vessel is also critical in order to keep the recirculating water nice and clean. This 25u bag is the last bit of filtration the water gets before it’s pumped back into the wash vessel for reuse. 

Here are the steps:


1. Ice cold RO water is mixed with cannabis material in the washing vessel that’s lined with a 220u work bag. This first wash is agitated for just a couple mins, as the first wash is going to take much less time to knock off the first batch of heads. It’s also going to collect the most contaminants. 

2. This water is drained out of the wash vessel and into the collection container that’s lined with a complete set of sieving bags. 

3. From here, the water drains into the recirculation vessel, which is lined with a 25u sieving bag. 

4. This first one to three wash, or batches of water that runs through the full set of sieving bags in the collection and recirculation vessels, is drained from the recirculation vessel as waste. This follows the traditional “batch” method of Ice Water Extraction, in which water is run through one time then discarded as waste. 

5. Fresh, ice cold water is added back into the wash vessel. 

6. After the first one to three washes, water is recirculated with the help of a chugger pump. Rather than passing through the 25u bag in the recirculation vessel and exiting as waste, these subsequent batches of water are pumped back into the wash vessel. 

7. The pump remains on, so that there’s a continuous flow of water through the entire system. The water doesn’t run through in batches, with a pause as waste water is drained and fresh water added back into the washing vessel. Rather, the same water is continuously pumped through the entire system from the wash vessel, through the collection vessel, and into the recirculation vessel. 

8. Once the material stops dumping resin (you can catch some water that’s coming out of the collection vessel in a mason jar and hold it up to the light to test for this) it’s time to end the run. 

9. Turn off the pump and allow the water to drain out. 

10. Thoroughly rinse all resin from each one of the collection bags! This step is critical. Read more about rinsing in our article How To Use Pressurized Water To Clean Contamination from Bubble Hash.

11. Collect the resin from all sieving bags.


Hash makers are both artists and problem solvers, and Closed Loop Recirculation is a great example of innovation in the process of Ice Water Extraction. Unlike traditional methods that waste water after a single use, the Closed Loop System keeps water continuous circulation, significantly reducing water wastage and operating costs. 

This method also requires less energy to chill water and minimizes the time spent refilling the agitation tank with fresh water and adding ice. While the initial one to three washes are drained like in traditional setups to eliminate contaminants, subsequent batches of water are continuously recirculated, enhancing efficiency in the hash-making process. And this also helps preserve the integrity of trichome heads during agitation, since the heads are able to exit the agitation vessel immediately, instead of floating around inside until that specific batch is complete. 

Overall, closed loop recirculation offers a more sustainable and efficient approach to Ice Water Extraction, benefitting both extractors and the environment.

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What is a closed loop recirculation system in Ice Water Extraction, and how does it differ from traditional methods?
A closed loop recirculation system allows hash makers to continuously reuse water during the Ice Water Extraction process of collecting loose resin or bubble hash. In traditional methods, water is discarded after a single use, whereas the closed loop system significantly reduces water wastage and operating costs by maintaining continuous water circulation.

What are the advantages of using a closed loop recirculation setup for washing bubble hash?
The benefits include less wasted water, reduced energy consumption for chilling water, lower daily operating costs, minimized time spent refilling the agitation tank with fresh water and adding ice, preservation of trichome heads during agitation, and increased capacity for starting material due to reduced ice usage.

What equipment is required for a closed loop recirculation system in Ice Water Extraction?
In addition to standard equipment such as mixing vessels and sieving bags, you will need a recirculation vessel, a chugger pump, and food-safe hoses as key components for the setup. These components facilitate the continuous flow of water through the system.

How do you configure a closed loop recirculation system for Ice Water Extraction?
The configuration involves a continuous flow of water from the wash vessel to the collection vessel and then into the recirculation vessel, where it passes through a 25u sieving bag for filtration before returning to the wash vessel for reuse. It is essential to use a 220u work bag in the wash vessel to keep larger contaminants out of the recirculating water clean.

When should the closed loop recirculation system be turned off, and what steps should be taken to complete the process successfully?
The system should be turned off when the material stops producing resin. To complete the process, you should thoroughly rinse all resin from each of the collection bags to ensure a successful harvest of bubble hash. This rinsing step is critical to maintain the quality of the final product.


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