Mueller/B & K 108-904RP Backflow Preventer-Vacuum Breaker

This really works. I got a cheaper plastic one first that kept leaking. Had no trouble with this one. I didn't even use the white plumbers tape. It makes a soft sound and does spray water when it activates, but at least I know its working. I have a soaker hose system setup for my raised garden beds with a timer. So the hose is on all the time under pressure. This goes off anytime the water is used in the house (sinks, toilet, shower, washing machine) so I know it really works. Just don't set it up somewhere you don't want to get wet.

This is a very well built device. It appears to work properly and it was very easy to install. I am not a professional plumber so I can't speak to its performance characteristics, but if I need a backflow preventer again, I will purchase this item.

This is the first backflow preventer I've used, but I do a lot of gardening and have a hose constantly connected to the outdoor spigot so I followed someone's advice and purchased this. I did not know about or expect the strong mist of water that periodically sprays out of the periphery of the valve, and it got me in the face right after I installed it :D. I guess that's just how a backflow preventer works... I assume it's releasing accumulated pressure. I will say that after I installed this, I started hearing a whining sound coming from the pipes in the house every time I flushed the toilet or shut off a running faucet. It took me several days of online research before figuring out that the backflow preventer causes this if the outside spigot is left on by creating a pressure differential between the outside hose and the indoor plumbing. I think it's harmless, but if your pipes start whining every time you use the water in your home, that's probably why.

Works great, does its job, great price, highly recommend everyone put these on your outdoor facets especially if you use a chemical sprayer of any kind attached to your hose. If you're spraying it when a line breaks or a firehose is used nearby on a hydrant it will pull all the water from your house and hose, including the chemicals, so please please get one of these and use it.

Does exactly what it is advertised to do. I installed mine on the black tank connection on our RV. Before, apparently putting water in the tank would build a small amount of pressure and water would spurt back out when I disconnected the hose, even with the black tank dump valve open. This prevents the back flow. It appears to be made well and I expect it to last a long time. Recommended

The unit feels solid and well made. However, the unit this replaced relieves the pressure much faster and has a lot more back flow coming out which makes me doubt the effectiveness of this replacement unit.

I purchased this and another brand to replace old units that were originally installed on our outside spigots. They were both leaking due to worn rubber washers. Unfortunately they use a break off screw that is permanently set in threads of faucet. I tried drilling out but was difficult as size is so small, also stripped out some threading because metal from the drill and old pieces get caught removing, luckily a lot of teflon tape sealed both damaged pipe threads. Needless to say I chose not to break the new installed screw off. Any additional damage would surely make the need to replace the whole valve. Not worth it. Hope these last a long time!!

Hard to mechanically test these aside from attempting to create a vacuum and confirming no water returns from the hose. There is a whine while in use, nothing awful. Does spray out a lot more water than another version I have (only when water flow downstream is halted such as a sprinkler timer or hose sprayer shutting off), NOT usable indoors for that reason.