Preventing deformation in your vessel
The BREWHA Jacketed Fermenters and Jacketed Boil Kettle and Cold Liquor Tank are designed to withstand a small amount of pressure (3psi in vessels and up to 5psi in jackets of 3-in-1, Boil Kettle, and Cold Liquor Tank, and 14.9psi in vessel and 7psi in jackets of 4-in-1), but are not designed to hold the kinds of pressure that can build up during fermentation if the CO2 is not allowed to vent, nor the kinds of pressure that municipal water is delivered at, nor a vacuum that could pull the walls in. The picture on the left shows deformation inside a fermenter when the jacket is pressurized to municipal water pressure (~70psi) and the picture on the right shows how the lid was deformed when too much pressure built up inside the fermenter during fermentation with the valve closed.
In order to prevent vessel deformation, all the following steps should be observed:
1. Do not put any restriction or closure on the blow-off port in the lid of the fermenter during chilling as a vacuum may form which could pull the walls in. (To prevent blow-off water from being sucked into the vessel, ensure that that volume of water in the trap, is less than the rising portion of your blow off hose can hold—before the water is sucked over into the vessel, air will enter the hose and be drawn into the vessel rather than the water; another preventitive measure is to put a small amount of Star San into the blow off water to prevent microbial growth.) Always keep a pressure relief valve installed on one of the lid ports.
2. Do not put any valve on the blow-off port in the lid during active fermentation (pressure may build up inside the vessel); pressure in main body of vessels should never exceed 3psi in 3-in-1 and 14.9psi in 4-in-1
3. Do not put any valve or restrict the downstream side of the jacket in anyway (since water enters at the jacket at the bottom of the fermenter, this would mean the top exit port)
4. Always use a non-kinking blow-off and drain hose that won't close and allow pressure to build up (or vacuum to form), and keep the hose as short as possible (the longer the hose, the more likelihood of kinking, closure or back pressure)
5. Ensure that the water can exit the vessel faster than it is being put into the vessel by keeping the exit fully open and restricting inflow water. (If water is rushing/spraying out the exit, it is very likely that pressure is building up.)
6. Install a water pressure regulator on the inflow side of the jacket to prevent inlet water from ever going over 5psi in 3-in-1 and jackets and 7psi in 4-in-1 (and a pressure relief valve can also be installed to relieve pressure if it exceeds the upper limit). This can be found at local hardware stores, online or can be purchased here.