Homemade Checkvalves

[WaterWolf]

What is the single most expensive piece on most APHs? The answer will usually be, the check-valves. These simple devices run at prices around $10 each and since APHs will often require two of these, almost half the money spend on a homemade might end up going into its check-valves.

In an effort to make homemade soakers more affordable in general, I have designed a very simple but effective check-valve, that can be built at home for the amazingly low cost of $3.60 each and takes only five easy steps to build.
These instruction will show you exactly how to build a 1/2-inch check-valve. You can vary the sizes of material for different diameter pipes.

The design and operation of it are basically the same as their store bought brethren. A short tube with a reducer at each end, a cone of rubber pressing on one of the ends from the inside and a spring that is pushing on the rubber.
The only parts you need are:

A 2-inch long section of 3/4-inch PVC.

A 3/4 x 2-3/16 x .062 compression spring.
I got those numbers off the box of springs. The first two indicate width and length of the spring in inches. The last number is how thick the metal is. These numbers should allow you to find the exact spring, but if you cant, just try to find a compression spring that fits well into a 3/4-inch pipe and is not too long.

A 1 1/4-inch "CampBell Hausfeld" bike-tire valve.
These are easily identifiable by a cone-shaped rubber gasket. The rubber is the part you really need here. If you can find another cone-shaped piece of rubber however, it may work just as well, but these seem to be perfect for my purposes.

And two, 3/4-Inch female-smooth to 1/2-inch male-threaded couplers.



1: Following the instructions on the can, PVC Cement one of the couplers onto an end of the PVC pipe. Let this dry.
2: Insert the neck of the tire-valve into one of the ends of the spring.



3: Slide this tire-valve and spring assembly down the pipe. The end of the spring should protrude about a half inch out of the PVC.



4: Glue the second coupler onto the other end of the PVC to close it up. Remember hold the coupler pressed onto the PVC pipe with your hands for about 30 seconds, so that they do not pop apart.

You have now built a fully functioning check-valve in only a few minutes and saved about $6.40 on your next project requiring one of these.



I have not actually used these in a homemade yet, but I did run some pressure tests and found that they worked beautifully.

[Specter]

thats genius. hope it works well.

just to help you identifying the spring:
3/4 x 2 - 3/16 x .062 compression spring.

The red number is the "diameter" of the spring - if you look down it, like through the hole, its the circle of it measured across. hope i explained that well enough.
blue is the length of the spring (you can compare it to your length of pvc)
green is the "diameter" (thickness) of the metal.
and the type of spring obviously is compression, i don't know if theres other types haha, i just know how to determine those numbers.

[WaterWolf]

Thank-you specter, I have edited my post accordingly.

Just in case it wasn't clear, they DO work. I have put them through tests that simulate a pressurized gun and they worked just fine.

[Ben]

I built a homemade check valve for my Vaporizer conversion back in 2004. Mine was similar to WaterWolf's and used a small rubber sheet and seemed to work great. I think a small rubber sheet would be cheaper than a tire valve, but I don't see any reason other than that to not use a tire valve. I like his use of the 3/4 inch to 1/2 inch adaptor though. That's a great idea.

Try out a small rubber sheetan WaterWolf. In my local are Lowes they like 1/4 inch thick and come in a 6 inch by 6 inch sheet. I don't know the price though, but you can make a lot of check valves from one shee.

Homemade check valves are good idea if you can make a quality one and manufactured check valves are not relatively cheap locally. This is a good quality design, so I recommend it, but only if check valves are expensive locally. The manufactured valves most definitely are stronger than these ones.

Where WaterWolf lives 1/2 inch check valves might not be available or be expensive. For the APH design I specifically used 1/2 inch check valves because they are a lot cheaper than the larger diameters. Here they are something like 5 to 6 dollars depending on various economic factors. Relatively cheap and very high quality.

Edit: I just checked the spreadsheet I made of APH parts for the new article. Check valves cost $5.85 here. Seems my memory is pretty good.

[Drenchenator]

Great check valve. It is simple and functional. Still, prices do vary a lot from place to place. Like Ben said, here in Maryland check valves are pretty cheap, but someplaces do have much greater prices. This valve should help a lot of people though.

[DX]

Your check valves in Maryland are the same as mine, $5.85. However, that figure is 3/4" for me - my 1/2" check valves are $5.35.

As posted at iScF, this homemade valve is very nice. I'd try a slightly weaker spring, though. You could also probably make it shorter with a shorter spring and different seal, but that's just me - I like to make homemades as compact as possible.

[Silence]

Fairly neat design, but there are some things you could do to make it more mass-producible. Take a look at Waterzooka's designs if you're interested.

1. Don't use rubber cones for the seals - who needs the stem? Waterzooka used rubber balls, which you can get in bulk. Of course, you may need an O-ring as well.

2. Use a less powerful spring (and if you make it shorter, then the entire check valve could be shorter). It needs to have just enough force to overcome the friction of the plunger. If you knew the friction of the plunger, you could divide it by the rate of the spring to figure how much you need to compress the spring when installing it. Still, this rate looks low enough.