Knife valve question

[Delphinus]

Ok this might just be a dumb question but I'm going to ask it anyhow.

I was thinking of using a knife valve (it's like a gate valve only it does up and down). I was looking at one and I could tell that the actual "knife" part (the plastic that goes up and down) is coated in some kind of lubricant.

Any idea what this lubricant might be? I'm thinking that this means the valve is not appropriate for use on an aquarium. The only times I've seen valves like this is on hot tubs, pools and RV toilet tanks, so I'm not sure. Its too bad because they are nice and compact otherwise.

[lastlight]

I have heard many times that there is metal parts inside the valve exposed to the water. Also have read they aren't as fine-tunable as a gate valve. They're cheaper but I'd personally go with the gate valve rather than take the chance.

[Delphinus]

It's more the space requirements and that I just need an open or close, that has me thinking of it. A ball valve is already too big to fit where it needs to go.

When I looked at one I checked for metal and didn't find any but that slimey residue makes me think its petroleum based and I guess that makes it a no go. Still want to know what it actually is though!

[lastlight]

If this is the one from western pump tony the guy told me he wouldn't use it in an aquarium. Can't justify that but it's what I was told.

[Delphinus]

That's what I thought, ok thanks..

[Funky_Fish14]

Tony... I use a number of(3?) PVC knife valves on a couple tanks, including my SW. Everything is doing just perfect? Just figured i'd toss that out there. The knife valves arent exactly the best though. and when you do 'close' them, they have the potential to leak.