I really hate to keep dragging this thread along, but it wouldn't make sense to make a whole new thread, so sorry for bumping (again).
Anyways, on to the update: I finally found a way to connect 2-liter bottles to PVC
without having it leak at all. I figured that I needed some way to go from 3/4" FHT to 1/2" MPT, so I originally used the plastic couplers that you have thus far seen (if you've read the whole thread; if you haven't, you can go back to see what I'm talking about). The problem with those was the fact that they were two parts that snapped together; the weak point was the area they snapped together at. I then though about using some kind of barb to fit into the cap of the 2-liter bottles that I would glue into place. While looking for said barb, I stumbled upon a (one piece!!!) metal 3/4" FHT to 1/2" MPT adapter. I was like, "This is what I've been looking for!" (not aloud, as I was in Home Depot at the time)
I bought three, along with a pack of hose washers, and some other things [#8 o-rings, a 1" coupler and misc. parts for repairing my pump].
So, if you're looking for a way to attach 2-liter, or any kind with the same mouth size, to PVC, I finally found a secure answer (I'm
very sure I'm not the first, though; I've read about others but they used things I didn't have. Rather than being custom made, I used something store bought).
In order to get the bottle to fit into the adapter, I needed to file
practically all of the threads off of the bottle. I then put one more hose washer (the flat ones are the best) in the adapter (there was one already included inside the adapter) and carefully screwed the bottle into the adapter. Since it was metal, it cut threads into the bottle, holding it securely while making a good seal.
Now, the pictures:
Line 1: My mini-water gun; my hand held nozzle trigger assembly with a 2L attachment - a shot of the 2L/fill attachment - the male QD on the end of my pump; it works for filling up waterballoons, too - my repaired pump; you can see the 1" coupler in the lower left.
Line 2: The 3/4" FHT x 1/2" MPT adapter - my 3-bottle water manifold, with attached hose and one-handed hose nozzle - my 3 bottles attached with adapters - my pump cap (simple, isn't it? the cool thing is it doesn't come off...)
The rest of the pictures are just of my pump and the check valves:
Line 4: inside a check valve to look at the spring (I used 3/4" female threaded plugs this time, instead of 1/2" slip plugs) - a view of the front of one of the sealing faces
In the last two pictures, you can see ho I flattened out the back of the metal piece I was using to hold on to the spring; I'm not sure whether or not it increases performance, but it's a lot more like a real check valve than using marbles or tire valves.
Questions and comments would be appreciated; I'm happy to provide more pictures or to explain anything in detail if you want me to. If you can't figure out what parts I used from the pictures (or if you want to know what specific brand/part I used), then you can just ask me and I'll make a parts list if you want one.