Tank valve upgrade

Ball valves by design are NOT well suited for this type of dirty environment....IE: hole thru ball valve TRAPS crud/stuff when closing

Sliding disc valves are used for a reason when handling this type of effluent.

Check out valves on any 'honey wagon' --- 'septic tank pumper' unit.,,,,sliding gate valves

Not sure what has happened to yours......?
Mine (4 of them) are still functioning properly after 10+ yrs of repeated use.
3 are cable operated and 4th is straight handle.

Beside the functionality issue there is the cost of a 3" brass ball valve which would be pretty expensive.

Aren't these valves rebuildable -- replaceable rubber seals?

Thanks all.

Don't have a problem with my valves (yet); was just thinking ahead. Figured the only reason a ball valve wasn't used was cost; didn't realize they gunk up. Just hate how flimsy the gate valves feel, and my black valve was installed at a really annoying angle causing me to have to crawl under the tt to get enough elbow grease to open it.

Guess I have to live with the tried and true!

I can see 2 problems using ball valves right away.

Problem 1 is cost even though there are plastic ball valves available.

Problem 2 is size. A standard sized ball valve for 3 inch pipe is going to take up a lot more space. Even with a standard 3 inch valve you will loose a lot of the high flow you need in order to get a good dumping of the tank. The waterway through a 3 inch ball could be as small as 2 inches. You can get 3 inch ball valves with a larger 3 inch waterway but they are going to be even larger because the ball will be larger but they aren't standard and therefore back to problem 1.

I don't see how they gunk up since the seats on both sides wipe the ball clean as it turns and stuff can't get around the seat and ball since there isn't a cavity that it can get into. I guess if you're eating your peanuts and sunflower seeds shell and all stuff could get lodged between the ball opening and seats hindering the valve from fully closing leaving a trickle but that can happen with the knife valve as well.

I don't see why the right ball valve wouldn't work, other than the physical dimensions - one that is "full bore" with an "easy turn" lever handle. The one in the photo is a compact version from PVCfittingsonline.com. One common complaint of these is how stiff they are to open/close but some are advertised as easy-turn. Cost is in the $30-50 range and the industrial/municipal versions for sanitary use are $200+. If they work for industrial/municipal applications then...

I'd consider using one if it would fit in an easily accessible location. The blade valve on our black or grey tank has leaked from day one and the dealer refused to look at it because it involved taking down the underbelly and came up with a lame excuse. KZ installed the sewer outlet under the slide and it is a pain (literally) to crawl under to attach the hose and I may re-arrange the piping some day and would be an opportunity to try a ball valve.