Over the four years we have had our 3625RE, our black tank sprayer seemed to spray less and less. The water flow diminished and eventually total stopped. After determining the vacuum breaker check valve was not broken, I figured I had a plugged up black tank sprayer and went to investigate.
Keystone used The Flusher system by B&B Molders on our rig. A diagram of is on B&B Molders website.
http://www.bandbmolders.com/pdf/B_BC...terSection.pdf
On our 3625RE, the black tank is up front on the door side. The sprayer is on the front of the black tank. I emptied the black tank and raised the front of the rig to make sure nothing came out when I removed the sprayer. I removed enough screws from the underbelly cover such that I could see the sprayer. I disconnected the water line, unscrewed the Spin Weld Sprayer (manufacturer name) and removed the three Phillips head screws. Using care, I pried up the sprayer plate with a screwdriver and then pulled the sprayer out of the hole in the tank. Pulling it out with my fingers was hard because there was a band of silicone sealant around the sprayer head on the inside of the tank, but I worked it out.
There are several small holes in the sprayer. I found some small grains of sand had plugged some of the holes and crap plugged others. I used a 1/16” drill bit to clean out the holes. The original holes were just slightly smaller than 1/16” so this bit enlarged the holes ever so slightly. I thoroughly cleaned the sprayer.
When reinstalling, I applied lots of non-setting water proof silicone sealant around the sprayer and on the plate. I did not have enough room or strength in my fingers to push the sprayer into the hole past the factory applied silicon sealant band on the sprayer head so I removed that band. I reinstalled the Phillips head screws although one screw hole was stripped and needed a larger screw. I applied non-setting pipe thread sealant to the Spin Weld Sprayer and reinstalled it. Reattached the water line. After the silicone cured, I ran water into the black tank sprayer and checked for leaks. There were none and so on went the underbelly cover. I bought garden hose washers with screen nets for the hose to keep from getting sand into the black tank sprayer again.
The result is a shower sound coming from the black tank a good flow of water and brown stuff coming out. More flow than originally, perhaps because of the slightly larger holes or because the sand had always plugged the holes.
In years gone by, I tried the Sewer Solution, but there are too many bends in the sewer plumbing for it to be effective. It will pump up a slight hill if needed. I bought a flexible wand sprayer to be used down through the toilet and it was marginally effective and much more hassle. I haven’t tried one, but he Flush King is supposed to quickly fill up the tank with water to draw out the contents. For me, the sprayer in the black tank is the most efficient.