When you get bored......

[Froggie]

Originally Posted by shimmy

Gate valves are not designed to be used as a throttling valve they are designed to be a 100% open or 100% closed, if you are looking for a valve that is designed to be throttling us a globe valve.
Now I am new to SW fish tanks but I do have a good idea of affects of flow through valves and I do know that when you use a gate valve you with wash out the seat on the valve then it becomes very difficult or impossible to get isolation.

I'd say you're absolutely correct in your comment regarding gate valves.
I think that one of the reasons that the hobby has taken to using them for this application is that small diameter CPVC globe valves are a specialty item. They're high cost and generally unavailable (IPEX doesn't even list them on their website). The same can be said for butterflys and they've some additional real estate requirements.

In all actuality ball valves have better throttling characteristics than gates... but try fine tuning a stiff plastic quarter turn ball valve.