One of the toughest things I've had to "discover" is information about gas lines, gas valves, etc. Not having gone through plumbing school where I'm guessing some of this is taught, I have found it difficult to locate information and help for those do it yourselfers. Of course that could be because gas is dangerous and if done wrong can render disasterous results. That brings me to the following disclaimer:

The information provided on this page is NOT to be taken literally. It is published here only for informational purposes and should never be used without proper professional assistance and certification. Anyone reading and subsequently using this information does so at their own risk and indemnifies me (Dave Gardner) for any missing, misleading or otherwise incorrect information. Information stated here is not necessarily fact based and is not applicable to any specific purposes.

Now that that's over with, let's get on to some interesting stuff.

When I'm building cook trailers I tend to always use 3/4" black pipe. I have found that 1/2" pipe sometimes limits the required amount of gas on higher BTU appliances. 3/4" pipe seems to always work well. There are actually tables you can use to determine pipe size based on the length of pipe and the BTU's of your appliances. Black pipe can be purchased almost anywhere. I get mine from a steel retailer and it comes in twenty foot lengths with no threads on it. One of my first investments was a pipe threader so I can put threads on 3/4" black pipe. I can thread almost any pipe as long as it is at least six inches long. Shorter than that and I go to my local plumbing supply store and buy "nipples" which come in lengths of 1, 2, 3, 4, and 5 inches with threads on both ends.

The picture at the right is a cool nipple tool I found at the plumbing store. It fits inside a 3/4" pipe and connects to a standard socket wrench. As you turn the wrench it expands and grabs the inside of the pipe. It saves a lot of screwed up threads when removing tight nipples.

When building your own appliances such as a BBQ or grill, the gas lines need to terminate into a "manifold". The manifold is a chamber where the valves are mounted and get their gas from. For what I do I generally use the same 3/4" black pipe as my manifold. It might be better to use a thicker wall square tubing but black pipe works for me. To make a manifold I cut the pipe to length and put threads on both ends. Generally the manifold needs to be secured onto something so I also weld one or more pieces of strap steel to it with bolt holes so it can be screwed down or mounted so it won't turn or shift. Just make sure any welds don't jeopordize the integrity of the manifold pipe to hold gas. Once this is done I drill my valve holes using a 21/64 bit. I then tap each hole (be carefull to keep them very straight) with a 1/8" pipe tape as pictured. Note the pipe tap sizes are strange, They are based on the old original diameter of the INSIDE of a steel pipe. Today the thickness of the pipes has substantially changed byut the pipe tape measurements remained the same. Therefore, don;t try and pull out your tape measurer and see it at 1/8 of an inch. It's more line a half inch.

Once the manifold is tapped out then the valves can be mounted. When mounting make sure to use yellow teflon tape. It's probably twice as thick as the white stuff and is meant specifically for gas fittings. There is also a pink tape but I haven't tried that. I have tried some of the pastes but I have had very bad luck with them. So I wrap it with yellow teflon and then put a light coating of True-Blue teflon paste on top of that. It seals nice every time.

There are many differnt valves you can find for your projects. Here's a picture of a few that I've run across. The one on the bottom with the blue cap covering the manifold nipple is the most common. Almost everything I do uses these. The other two are just a little different. The one in the middle left side clamps to the manifold and a rubber washer seals it. This type is used on a lot of cheaper commercial gas appliances. The one at the top right side has an orifice straight up from the manifold nipple. I personally like the 90 degree design of the standard valve. Each valve has three main parts, the manifold nipple (which screws into that 1/8" pipe thread we discussed earlier), a knob end where the on/off knobs mount to, and the orifice nipple where the orifice usually mounts. In this picture all three valves have the orifices already mounted to them but they are removable.

Here is a picture of the standard valve with the orifice removed. The plastic blue cap is on just to protect the threads during shipping. It is removed and thrown away when installing the valve. Thus far I've talked about mounting the valve directly to the manifold. In reality because it has a standard 1/8" pipe thread mount, it can be screwed on to the end of a piece of copper tubing with a 1/8" fitting. The othe end can be connected to your gas supply. Also the orifice end can also be extended using copper tubing and 1/8" pipe thread connectors. The orifice controls the final gas flow to your burners. Orifices must be sized according to the type of gas used and the BTU's needed for a burner. The valvel shown here has a "needle" or stem inside the orifice so the orifice hole can be adjusted but tightening it down further. This is one way to size the orifice and allows you to "tune" it once it is connected to your burner. I personally prefer to pre-drill the hole to the right size and make it non-adjustable. Then ongoing tuning is never needed.

Here are some standard orifices arranged so you can see the hole in the end. The dark one on the left was used in a high BTU burner. It has the largest hole (#37 drill or .104") of the samples so it provides the most gas to the burner. The next one is a standard natural gas orifice. Natural gas requires more flow than propane, therefore the holes are bigger. This one has a #45 drill or .082" hole. The third one from the left is a standard propane orifice which has a #54 drill hole or .055". The one on the right has a very tiny hole which could be used as a pilot light. I buy them with this size and then drill them out to what I need. So it's easy to take the orifices off a propane device, drill them out larger and place them back on to convert it to a natural gas appliance. To convert a natural gas appliance to propane requires you to get new orifices as then need a smaller hole. If you get real lucky and have an adjustable orifice then it's very easy to just adjust it accordingly.

Here is a picture of a few other orifices from other appliances. The one on the right is a standard orifice with a 1/8" female pipe thread on the inside. The middle one fits almost the same but was made longer to ensure it doesn't slip out of the burner orifice hole during travel. The one on the left is from a commercial convection oven that needed some serious fire power.

Before we move on, one more note about the valves. Once I mount the valves on my manifold and bolt the manifold in place, I usually create a "cover" plate that has holes in it for the knob ends to go through. When you do this be careful that the cover plate DOES NOT rub on the valve knob shaft. The shaft should turn free and clear without any obstruction. The actual gas flow inside the valve is controlled by a cone shaped pice connected to the knob stem. If you put any pressure downward or sideways on the stem it will make it so the valve always runs and your burner will never shut off. It also will quickly ear a significant groove in the shaft as the valve shaft is usually made of soft brass.

Once all your gas lines are ready and your manifold has been built and valves installed, you can (and should) pressure test. This will let you know if you have any leaks. The picture at the left is my pressure tester. It consists of a 3/4" pipe with an air pressure gauge and a valve stem attached to it. I connect this to the end where the gas comes in and use a bicycle pump to fill it to between 3-5 lbs of pressure. Your system should hold the pressure for days. If not, check it all again. If you use unions the tighten them harder. You can also use soapy water and a small paint brush around each coupling to locate leaks. Make sure it is solid before you connect it to the gas.

The orifice goes directly into teh end of your burners. Here is apicture of one such burner. Each burner usually has an adjustable plate (see the phillips screw) by which you can adjust the air to gas ratio. I'm no expert on what to look for when adjusting this. There are several good write-ups on the web that explain it better than I can here. I just know that if you close off the air too much then the gas burns way to rich and whatever is on top of the burner turns black with soot. Therefore I lean towards much more open than closed. The one shown in the picture seems close but I might open it a bit more. But then that depends on your burner.

My personal favorite burner is a standard 24" three row cast commercial burner as shown above. These cost me about $11 each. One end has the orifice hole and air adjustment and the other has a 1/4" post which can be used for mounting. I use these for BBQ and griddles. When using them for a BBQ or a thin griddle plate, I place a pice of 1 1/2" angle iron just above the burner to deflect the heat out so it heats an area evenly. With these burners the orifice can come directly from the valve and into the burner. The valve can actually help support that end of the burner. With a stove burner the valve is usually a distance away from the burner and so the orifice will need to be extended with copper tubing.

The knobs are actually the most expensive part of the whole process. Good chrome plated steel knobs are a little expensive. They are also the first to get lost on a trailer. There is a lot of differnt types availabel including many plastic ones. I tend to like the steel ones as they have a set screw and I don't loose as many.

So there's my wealth of information on gas. Over the year's I've learned that it's really not as "mysterious" as people paint it to be. I've been shopping for gas parts where I can't tell them what exact model of range teh part came from. I find some places to be very helpful and others that won't even sell to me. But just by playing around with it I can now take almost any gas appliance and convert it from Natural to Propane or the otehr way around. When building cook trailers with whatever you can find these skills come in rather handy. I hope this has proven somewhat useful information. Hopefully I'll get more examples and pictures up soon.