GASHER 2PCS Automatic Air Vent Valve, 1/2" DN15, Brass, Globe Valve, For Solar Water Heater And Hvac System

Excellent craftsmanship...and two for the price of one great deal.

These are nice compact air vents and allow small amounts of air to burp out when mounted at a high spot in your water system. Not much pressure is required to purge, but neither is the air let out very fast. I'm using this to reduce the air which gets past my pump before it gets to my filters, since air in the filters can slow them down considerably. Be aware they are 3/4", but parallel or straight threads, not standard NPT tapered. DN20, as described. With enough teflon tape and force, they can seal on NPT fittings, but should be used with proper adapter. Brass construction feels solid. There are Chinese characters cast prominently on the cap which were not evident in the listing photos.

So this is basically an air/liquid separator. As long as there is pressure in the system, any air that finds its way to this vent valve will cause the valves internal float to drop which opens a small port for the air to escape. Once the liquid reaches the float and it rises, it will close the port and stop any liquid from being able to escape.This does work well, however, depending on how large of a system and how much air you are talking about, it could take quite some time for the small exit port to allow the air to escape.The knurled knob (covering the exit port) allows you to choose if that separation occurs or not. If you keep it closed, it will not purge out the air. It functions as a separator only if the knob is opened.My intentions are to try this in a camper just after the water heater on the hot water line. When water is turned on to the camper, this will allow the tank to fill automatically. This can help prevent damage to the water heater if the heating element/burner is turned on while the tank is empty. I will likely leave the knurled knob off and connect a small tube to exit the outside of the camper...just in case there is a failure of any kind. This will also assist in draining the tank if there is no pressure on the line and a drain valve is opened. Most campers have check valves at the water inlet connection to prevent water from exiting the system if the internal pressure exceeds the external pressure.I have been doing this very thing with an inverted "flapper" style check valve for years in a vacation home. While my version will allow the tank to fill very fast, it does close very hard when the tank is full. I have never like the sudden spike in pressure from a totally open line to a instantly closed one. Hopefully this will be the compromise I have been looking for.

The GASHER Automatic Air Vent Valves appear to be well-made and suitable for their intended purpose. While they may not be constructed from solid brass, they still exhibit a level of quality that suggests they will perform effectively in my closed-system tankless hot water circulation setup. These valves offer a cost-effective solution for maintaining proper air balance in water heating systems, making them a practical choice for both residential and commercial applications.

The product was very well packed and arrived safely, with no damage. While most people may use these for high pressure situations, like well-water storage tanks, I actually need them for low pressure situations, where air entrapment can cause tanks to stop filling. In many rural areas, like ours, we are reliant upon rainwater catchment tanks for our water. The fill lines sometimes cross over uneven terrain where high spots exist. In these high spots, air will accumulate and eventually impede the waterflow. If the plumbing elevation cannot be adjusted to remove these high spots, the next best solution is to allow the air to escape, but not the water. These air vent valves are great for this situation, because one can install a saddle tee on the feed line (typically a 3" pipe) and the Air Vent Valve on top of that, using a 1" extension pipe. As rainwater fills the lines, the air is pushed to the high spot and slightly pressurized by the weight of the water. This tiny amount of pressure forces the air out through the vent valve, until the water reaches the piston and the float engages, closing the valve. Water is life! Great product.