THR water gun

[Silence]

Even better, drill a hole in a sheet of plastic and tape a rubber sheet over it, on the inside. It's essentially a sleeve check valve. Sleeve valves, as used in inflatable balls, use a metal inlet needle that is inserted into a thin rubber tube. The pressure from the air holds the rubber onto the tube. When you pump whatever's attached to the needle, air escapes from a hole in the side of the needle and slips out to the inner area. And as a bonus, the air pressure squeezes the opening shut when the needle is removed.

So you could have a plastic plate with a rubber (or plastic bag) sheet over a hole in it. Air coming through the hole pushes the rubber sheet off the surface just enough to make it through. Air can't go back, and the pressure pushes the sheet against the hole. Of course, this would work best on a flat or convex surface, unlike the concave surface of the inside of an endcap.

[aEx155]

Originally Posted by SilentGuy

Even better, drill a hole in a sheet of plastic and tape a rubber sheet over it, on the inside. It's essentially a sleeve check valve. Sleeve valves, as used in inflatable balls, use a metal inlet needle that is inserted into a thin rubber tube. The pressure from the air holds the rubber onto the tube. When you pump whatever's attached to the needle, air escapes from a hole in the side of the needle and slips out to the inner area. And as a bonus, the air pressure squeezes the opening shut when the needle is removed.

So you could have a plastic plate with a rubber (or plastic bag) sheet over a hole in it. Air coming through the hole pushes the rubber sheet off the surface just enough to make it through. Air can't go back, and the pressure pushes the sheet against the hole. Of course, this would work best on a flat or convex surface, unlike the concave surface of the inside of an endcap.

That sounds like a great idea, but I don't think this would work in this situation. Since there's no pressure in the reservoir, there wouldn't be anything to hold the rubber sheet against the hole, and it would just fall open and let some water out. The reason for the check valve is to let air in and keep water out, not pressure; if there were pressure, then this might work; but there isn't, so it probably wouldn't.

The spring check valve Ben's using works because it's held closed by a spring; no water gets out but air can get in.

Also, I think it would work better on concave rather than convex; if it convex, it's like having the sheet on top of a bump; it doesn't really work. If it's concave/flat, then there's a place for it to sit on and seal.

Just wanted to add my thoughts...

[Specter]

I was wondering how much you spent on that mini check valve. I know it can't be much because I saw them on www.usplastic.com for cheap but I can't seem to find them again

[Ben]

That sounds like a great idea, but I don't think this would work in this situation. Since there's no pressure in the reservoir, there wouldn't be anything to hold the rubber sheet against the hole, and it would just fall open and let some water out. The reason for the check valve is to let air in and keep water out, not pressure; if there were pressure, then this might work; but there isn't, so it probably wouldn't.

If you put it on the inside and had some mechanism to close it, it should work. Seems simple enough. This method was so cheap I don't think it needs to be changed though.

I was wondering how much you spent on that mini check valve. I know it can't be much because I saw them on www.usplastic.com for cheap but I can't seem to find them again

The small check valves are McMaster-Carr part number 7757K13. They cost $3.38 each there. I absolutely love them.

Attached are some images of work done so far. I need to buy some epoxy to permanently stick the check valve on the cap, a small tubing barb for one part, and some LRT, but aside from that I'm good.

[Specter]

was there shipping costs for that? because I found a similar valve on usplastic.com part #64001 and its $1.69 but for me (if i were to get it) shipping is $7.35

[Ben]

I bought it with a few other items so the shipping costs wouldn't have been realistic for just the valve alone. McMaster-Carr usually has very reasonable shipping. I highly doubt it will be that high for a few tiny valves.

[Specter]

oh, ok. I was just wondering. Thanks.

[Silence]

aEx, even in a reservoir, a rubber sheet might do the trick. If the hole's in the top of the tank or otherwise above from the waterline, as usual, you already have fairly good protection against water leaking out. Slap a sheet of rubber on top and that's just a bonus layer of protection. That said, I admit you'd need either a convex surface (so the rubber stretches a bit) or more pressure for a real seal.

Ben, what else have you used the small check valves for? Would they work well enough for pumps?

[aEx155]

Originally Posted by SilentGuy

Ben, what else have you used the small check valves for? Would they work well enough for pumps?

I believe he replaced one of his larger ones with a smaller one. Technically, though, you could use them instead of regular check valves; it would make it cheaper if the flow was enough (and you had a way to get around shipping).

[Ben]

I assume they would work fine for pumps. I've replaced one of the pump ones with a small one because it would save space. The flow should be adequate but if it's not I'll let everyone know.