Here's a review of how I used a home-made manometer to assist me in converting my my Member's Mark BBQ Grill from Propane to Natural Gas - you don't need to buy a fancy-smancy digital manometers. I needed to know the Natural Gas pressure. The local gas company told me it was 6 inches of water pressure coming out of the regulator; but I had heard that one gets various answers from the gas company, and there is not a manometer on the regulator to review.

So I figured I'd just measure it myself with a home-made water manometer as shown in the attached pictures. I got everything at Home Depot; the clear plastic tubing cost a dollar and I bought the clips for about fifty cents. NOTE: The diameter of the tubing does NOT matter - pressure is pressure, so the readings will be the same regardless of the diameter. If you want to hook it directly up, you will probably need a metal coupling. But this is not neccessary with the Member's Mark BBQ Grill as it is easier/better to simply remove the side burner (undo clip and slides off), and plug the tube into the orifice. Use a metal O-Ring for a tight seal. BTW, whatever approach you use, it's a good idea to measure it before you go down to the hardware store to buy your manometers stuff (or bring a piece of doable) since there are a bazillion different sizes, and it sure is nice to buy the right size first.

Once you have the water manometer built, fill a cup with water and couple drops of food coloring and fill up the tube. Make sure the board is level, and in addition to the 1" markings, I recommend taping a piece of paper to it. Then mark the "zero" position, turn on the gas supply, mark the new position, measure how many inches up the new water level is, and multiply that by two ... and you got your gas pressure! ;-) For bonus points, then turn on the burners, and see what type of pressure drop you get. Remember, multiply by TWO, since the pressure is the difference in height between the lowest and highest part of the manometers.

I measured just over 11" with propane ... which is very consistant with what just about everyone says should be the regulated pressure. And I measured 6.5" Natural Gas. However, I initially measured a drop to 3" when all three main burners were on, which indicated that I had insufficient flow to the grill. A LOT more details on that can be found in the LP->NG conversion web page.

You can also review if you have any leaks in the grill itself so you don't have to buy a new house! Check to make sure the gas supply is OFF, and then the side burner control to HIGH. Then open one of the MAINS to HIGH; and then close it when the manometer is in a stable position - it should be level, if it's not, you goofed something up. While leaving the side burner control on HIGH, turn the gas supply ON. Manometers should respond and eventually stabilize at the regulated gas pressure. Mark this location, and then turn the gas supply OFF. The manometer reading should NOT move; this is basically testing everything downstream from the gas supply valve up to control valves. Note that it does not test any leaks past that; such as the tubing to the back burner or the orifice's themselves - you will need to use the soapy spray approach on those. Standard disclaimer applies, but nothing is completely airtight - I feel that if you take at least 5 minutes to bleed off an inch of pressure, you are probably OK.
Manometers with direct Coupling to Gas
manometer 1
Plugged into Side Orifice (MUCH better/easier)
manometer 2
Use paper/tape to measure pressure accurately
Picture shot from above - note parallex affects
manometer 3

Gas OFF - "zero" reading
zero reading
Gas ON - 6.5" WC
6.5 reading
2 Mains ON - 5.2" WC
5.2 reading

Dirk reviews Propane Pressure
measuring LP pressure
Measuring NG Pressure
measuring NG pressure
Dirk is lotsa help!
dirk helps

So who needs a digital manometer when a home-made water manometer will do the job! ;-)

©2003-2007 - Alek Komarnitsky