HOW TO: Gas Conversion


 
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Chris Allingham

Chris Allingham

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Over the past few years, we have seen more and more people refurbishing vintage Weber gas grills, and along with this comes an increasing number of questions about gas conversion between liquid propane (LP) and natural gas (NG). In the old days, Weber would sell you the parts needed to convert an LP grill to NG or vice versa. Today, Weber is very clear that they don't want customers doing gas conversions, nor do they want you moving grills between countries and attempting to adapt from one country's gas standard to another. When done wrong, these modifications can damage the grill or cause property damage, personal injury, or even death.

As a forum, we see many people who think conversion is as simple as buying and installing a third-pary DIY conversion kit. Often times these conversion kits fail. They include questionable parts that when installed result in roaring burners that can't be controlled.

Or maybe you read that you can drill-out small LP orifices to make them large NG orifices, or that you can buy orifice "spuds" and drill them to the desired size to convert a NG grill to an LP grill. In order for this to work properly, you need the right kind of gas valves in your existing grill. Do you know what kind of valves your gas grill has? Are they fixed spool gas valves or continuous spool gas valves? And how can you tell the difference between the two? If you don't know what you're doing and don't have the right information, at best you end up with a grill that doesn't work properly, and at worst you end up with a grill that is dangerous to operate.

Our advice is that you shouldn't mess with replacing individual orifices, valves, etc. After lots of wasted time and money, many people end up with grills that do not work properly, like the one shown in the photo below.

Our stock answer to the question of how to convert a Weber gas grill is this: Replace the entire manifold assembly with one designed for the desired fuel type. Yes, replacing the entire manifold is more expensive, but it's a project that is within the capabilities of many owners and likely ends with a successful and satisfying outcome.

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Photo Credit: TVWBB member JoeR

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Replacing Your Manifold

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Photo Credit: TVWBB member Bruce

The manifold is a solid metal pipe that connects to the gas supply and fills with gas. Control valves are installed at intervals along the length of the manifold, one for each burner. On one end of the control valve is the knob and inner workings that you turn to adjust the amount of gas entering the burner. At the other end of the control valve is a brass fitting with a very small hole in the end called the orifice. The orifice is inserted into the burner tube. Gas exits the orifice into the burner. The orifice hole size limits the maximum amount of gas that enters the burner. The hole size is determined by many factors including type of gas, the gas pressure, and the BTU (British Thermal Unit) rating of the burner. The inner workings of the valve, the dimensions of the orifice, and the size of the orifice hole are carefully designed to work together to deliver the correct amount of gas to each burner to achieve the desired BTUs. This unique combination of control valves, orifices, and burner BTU means that you cannot typically swap control valves and orifices from one brand of grill to another and not even between different grill models within the same brand.

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Photo Credit: TVWBB member RayM

The good news is that since Weber makes both propane and natural gas versions of its grills, the easiest way to do a conversion is to replace your grill's manifold with the one made for the other fuel type. For example, if you've got a Genesis 1000 propane grill, you need a Genesis 1000 natural gas manifold. Weber won't sell it to you, but you can buy one from a third-party parts supplier (expensive) or get a used one from a junked Genesis 1000 natural gas grill (cheap). Alternatively, if you've got a natural gas grill, you'll need a propane manifold from the corresponding grill.

The manifolds are easily swapped out, and the replacement manifold includes the correct valves and orifices for the new fuel type. Weber owners manuals and other support documents often include assembly instructions or manifold replacement instructions that help illustrate the process of removing and reinstalling a manifold. You can download these by model name or model number at weber.com.

In addition to the manifold, you'll need a hose to connect it to the fuel source. If you're converting from propane to natural gas, you'll need a natural gas hose. Amazon has lots of options, but this one should get the job done: https://amzn.to/3fE6tLV If you're converting from natural gas to propane, you'll need a hose/regulator kit. These can vary depending on your grill's model number. Many of the old Genesis 1000-5000 and Spirit 500/700 grills with 1/8" NPT male thread used the Weber 7503 hose/regulator. You can find several third-party versions of Weber 7503 on Amazon: https://amzn.to/2F3M9He But do your research and buy the hose/regulator kit that is compatible with the propane version of your grill model. Compatibility has to do with the fittings on the hose and the flow capacity of the regulator, ensuring that it can supply the maximum amount of propane needed to run your grill with all burners on HIGH.

Use Pipe Dope To Seal Gas Connections

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When screwing a new gas hose fitting into a manifold, you'll need to apply pipe thread sealant to the connection. Rectorseal No. 5 works for both propane and natural gas connections: https://amzn.to/2Fkg0vj

Note that if you're using a 1/8" Male NPT to 3/8" Male Flare fitting to connect a 3/8" propane regulator hose to a grill, apply pipe dope only to the 1/8" Male NPT threads that screw into the manifold, not to the threads on the flare fitting.

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1/8" Male NPT on left, 3/8" Male Flare on right. No pipe dope on the flare threads!

The flare fitting is a metal-on-metal fitting that seals when tightened without pipe dope.

Converting To Natural Gas? Check Your Gas Pressure & Install Correct Piping

When switching from propane to natural gas, the first thing you should do is visit weber.com and download the owners manual for the natural gas version of your grill model and year. It will help you complete the following steps.

Natural gas pressure in most homes runs between 3WC and 7WC. WC stands for "water column" and is the unit of measure for gas pressure. Weber designs natural gas grills to operate within this range of pressures. The owners manual for the natural gas version of your grill will include a specification about water column pressure. For example, from page 15 of the 1997 Genesis 1000 LX natural gas manual:

"This barbecue is designed to operate at 7 inches of water column pressure (.2526 psi)."

If you have any doubts about whether your home's natural gas pressure is adequate for your converted grill, have it checked by a gas supply professional. If the pressure is too low, the grill won't function properly. If it's too high, you may need to install a pressure regulator on the supply line, another task for a professional.

You will also need the correct pipe installation to connect the new natural gas hose from your converted grill to the gas shut-off valve in your backyard. The owners manual for most Weber natural gas grills includes instructions and a diagram showing the pipe nipples and reducing couplings needed between the shut-off valve and the quick-disconnect where the grill's hose plugs in. Yet another task for a gas supply professional.

If you're converting from natural gas to propane, you don't have to worry about any of the above. Weber propane grills expect 11WC of pressure and the correct propane hose/regulator will provide this pressure to the grill.

Connect Propane Grill To House Propane Tank

This is a job for a gas supply professional and eliminates the need for using 20 lb propane bottles. Some propane suppliers discourage it, but Weber sells a bulk propane installation kit for many of their propane grills. At time of writing, they can be purchased from Weber Customer Service at 800-446-1071 for $50-$80 depending on the grill. Have your grill model and serial number ready when calling. Weber recommends that the kit be installed by a licensed installer, plumber, or authorized gas professional.

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Liquid Propane and Natural Gas Are Not Interchangeable

To the average Weber grill owner, it seems like converting from LP to NG or vice versa should be easy--you're just changing from one type of gas to another. However, propane and natural gas are not interchangeable fuel sources. Propane is delivered at higher pressure and contains twice as much energy per cubic foot as natural gas.

Imagine filling your Honda Accord with racing fuel. Or filling an Indy race car with unleaded gasoline. It's not gonna work, at least not without some serious modifications!

How Does Fuel Type Affect Grill Parts?

Weber uses a series of control valves attached to a manifold to deliver gas to each burner tube. A control valve consists of a brass valve body, a valve cover, a valve spool, a valve stem, and a control knob. The control knob and valve stem engage the valve spool inside the valve body. The valve spool is a cone-shaped piece of brass with a series of machined holes and channels. When you turn the control knob, the valve stem rotates the valve spool, varying from OFF to HIGH to MED to LOW the amount of gas passing through the valve spool to the orifice, where it exits the control valve and enters the burner tube. The orifice is a brass fitting that screws onto the end of the valve body where it enters the burner tube. It has a small hole in the center that limits the maximum flow of gas into the burner tube.

To account for the difference in pressure and energy per cubic foot between LP and NG, Weber uses different control valves for each type of grill. Specifically, the difference between these control valves is the size of the machined holes and channels in the valve spool and the size of the orifice hole.

For example, if Weber wants a burner tube to achieve 10,000 BTUs using LP, they choose a control valve containing a valve spool with specific-sized holes and channels and an orifice with a specific-sized hole. To achieve 10,000 BTUs using NG, Weber chooses a control valve with larger holes in the valve spool and orifice. This allows more natural gas to enter the burner tube to achieve the desired BTU level.

Long story short: LP grills have smaller valve spool holes and smaller orifice holes, NG grills have larger valve spool holes and larger orifice holes.

Here's a photo showing a NG valve spool on the left, an LP valve spool on the right. Note that the two indentations and the small hole in the center of each indentation are larger in the NG valve spool than in the LP valve spool. Also, the channel is shorter in the NG valve spool, longer in the LP valve spool.

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Photo Credit: TVWBB member G Schafer

Here's a photo showing a Genesis 1000 natural gas orifice on the left and the propane version on the right. Notice the difference in hole size.

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Photo Credit: TVWBB member Bruce

Fixed vs. Continuous Valve Spools

Here's where things get confusing. There is a variation when it comes to valve spools. The valve spools shown in the photo above are fixed valve spools. Each hole corresponds to one of the "HIGH/MED/LOW" settings for the burner.

The valve spool shown below is a continuous valve spool. It has a series of spiral channels machined into the spool. This design allows for infinite burner control similar to a household gas cooktop and has the advantage of working equally well in both LP and NG grills. The bad news is that Weber has purchased control valves from various suppliers over the years, sometimes with fixed valve spools and sometimes with continuous valve spools, so it can be hard to know exactly what kind of valve spool your grill has without disassembling the valve body and examining the valve spool inside.

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Photo Credit: TVWBB member BHeemsoth

Conclusion

It takes a lot of things coming together just right for you to modify the bits and pieces inside your grill to convert from LP or NG or vice versa. For best results, you've got to have the right valve spools and you've got to have the right sized orifices. We've seen enough problem reports from people here on the forum to know that your best chance for success is to simply replace the entire manifold...then pass along your old one to someone that needs it for their conversion.

Good luck!
 
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I've converted from LP to NG by swapping the entire manifold as well. It is a lot easier than getting into the valves, and a lot more peace of mind that way too.
 
@Chris Allingham and @THyde, are you guys using a regulator on your NG line? There was one already installed from the previous owner's NG grill and I just ended up using it my Genesis 1000. The flames are steady and controlled correctly by the knobs, but it seems that they are a little weak. That might be normal for NG though, I've never used it before. The manual states it can operate at 7WC just as Chris mentioned in the original post. I'm not sure if the regulator I am using is preventing that from happening.

I have included a picture, any help is appreciated!IMG_1105.jpg
 
I'm not using a regulator, and I find that if I turn the grill on full blast, it gets extremely hot extremely quickly, but not too hot. Hot enough to barely pin the thermometer. At low, I do fear that I'm close to flickering out sometimes, but I have to get back into the valves. I may have globbed too much brake lube on them and plugged one or more holes. My valves are set position type. I want to disassemble them and clean them out with a toothpick one day. I want to do lots of things one day, but I may get around to double checking my valves.
 
If you have flames lit on low, and sufficient heat on high with the regulator, I see no reason to remove it. Our house (93 years old) had an existing NG line to the grill area, I added a local shutoff (there is another local shutoff in the basement) and then the grill, there is no regulator in my setup. I haven't had any problems and have good temperature range. Again, if the regulator is already installed and you have no problems on either high or low end, I'd leave it. Likewise, if it's not already inline and you have same problems, I'd install it. If somebody handed me one, I guess I might put it in line, but that would involve some pipe work that at this time is not necessary.
 
Thanks for the input guys. I tried it without the regulator and it seems much more in line with the performance I had when it used LP as a source. Flame was much stronger, but still controllable. I think I am going to use it without the regulator for now.
 
Your Genesis 1000 if it's TRULY a factory made NG grill is not made to use a regulator. It is rated to run at 7"WC. Your regulator is trying to make the grill run on half that pressure. It will work but not really well. It could be the previous owner had it there because their old grill may have required it. I.E. many like Broilmaster use one, and so on. But for your Genesis the only reason a regulator would be required is if your home is plumbed with high pressure nat gas. Not common but I have seen it
 
LMichaels said:
Your Genesis 1000 if it's TRULY a factory made NG grill is not made to use a regulator. It is rated to run at 7"WC. Your regulator is trying to make the grill run on half that pressure. It will work but not really well. It could be the previous owner had it there because their old grill may have required it. I.E. many like Broilmaster use one, and so on. But for your Genesis the only reason a regulator would be required is if your home is plumbed with high pressure nat gas. Not common but I have seen it
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This seems to fit perfectly with with my findings. The previous grill was a smaller, two burner Dyna Glo grill. My Genesis 1000 seems to be firing on all cylinders without the the regulator. Thanks for the advice!
 
You're welcome. A good indication of your house gas pressure is if you have black iron pipe odds are it's 7"WC from the meter all the way through the house. If you have small diameter copper than it's high pressure gas and you need a regulator at every outlet. Again this is just generalization from my personal experiences. YMMV and I ALWAYS recommend you use a manometer
 
LMichaels said:
You're welcome. A good indication of your house gas pressure is if you have black iron pipe odds are it's 7"WC from the meter all the way through the house. If you have small diameter copper than it's high pressure gas and you need a regulator at every outlet. Again this is just generalization from my personal experiences. YMMV and I ALWAYS recommend you use a manometer
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This is great information. I do not have a manometer, but I do have black pipe gas lines, and since I have not had any problems with the fuel supply I will be content that the grill is connected properly. Plus, the connection was already there, and I am sure that the line was run by a professional. I realize that doesn't mean all that much, but in this case it kind of does due to the level of work generally speaking that I come across in the house. Plus what I am reading is that there will be either high pressure gas (which we definitely don't have) or 7"WC, with a regulator the only thing I could do is decrease the pressure, and judging by the flame output that is not necessary.
 
Yeah. Funny on my house the ONLY work (gas, electrical, plumbing) that is done properly is what was NOT done by a "professional" but by myself and my buddy. I think the contractors on my house when it was built were drunk. My plumbing looks like something the 3 Stooges did in A Plumbing We Will Go
 
Thanks for the great write up!! I stumbled across this and the "My grill gets too hot" post because it happened to me. I found a super cheap 2012 NG Summit S-470 on CL and ordered a LP conversion kit off eBay. ( I really wish I had found this forum before I jumped on the grill, oh well, was a great learning experience... ) After changing out orifices and regulator, I too had a kiln (700F w/ main burners set to low). I disassembled one of the valves and sure enough it has a fixed/stepped cone with big orifices. The eBay seller really pushed back and comically tried to discredit this forum, smh. I checked the BTU gas tables and orifices we're drilled to correct size for 12k BTU, 11"WC ( unfortunately I don't have a manometer to validate new Weber 7627 regulator was doing its job). So I put it all back to NG and resold it on CL. I didn't feel like putting more money into a manifold swap. Besides, I'm happy with the simplicity of my 2003 Genesis Silver B, especially after this ordeal.
 
And if you get past all that, then you have the cook box panels to worry about on the Summit grills. I think your best decision was going back to the Silver B for now.
 
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