Using a Homemade Manometer

Our new clothes dryer isn't working and it was suggested that we didn't have enough gas pressure. It's a mystery: could a brand new dryer be at fault, or is it the freshly installed gas line, or the main gas feed to the house.

USA residential natural gas pressure is often measured in inches, that is, inches w.c. (inches, water column), or wci. It sounds like a weird unit for pressure (like, why not use PSI or some scientific SI unit), but the beauty of this archaic unit of measure is the simplicity of the tool used to measure gas pressure: a manometer.

All one needs is some oversized fish tank plastic tubing, a few ounces of water and an inch ruler. It took me less than 5 minutes to make a working manometer out of random junk in the garage.

Manometer Photos

Here's the finished manometer being used to test gas pressure in the laundry room (dryer) and the garage (water heater).

Pressure Readings

Below, the first photo shows a zero reading (gas value off). The next photo shows a several inch reading (gas value on). The last photo shows detail of the measurement; about 3 1/2 inches. The gas pressure is then two times that (since one water column goes down as much as the other column goes up and the pressure is proportional to the difference in elevations). So the gas pressure here is about 7 inches. This level seems normal.

Shared Load Pressure Drop

Below are a series of photos showing slight pressure changes when the six-burner kitchen stove and/or the house furnace is turned on. It's about 7 inches with no load and goes down to 6 1/2 inches with both the stove and furnace on full. This variation seems normal.

off on stove furnace stove+furnace

Double Check

Just to be sure the manometer is working, I brought it over to another house. The gas pressure there also is about 7 inches.

Actual Pressure


PSE (Puget Sound Energy) was here today to make official measurements of the pressure. They reported 6.8 inches. So it looks like my homemade manometer is right on. Since the gas line is fine; it must be a problem with the dryer.


Replacement new dryer installed today and it works fine. Mystery solved: PSE gas pressure is fine, new gas line is fine, the first dryer was DOA.

Parting Shot

Just a few ounces of water, plastic tubing, and a ruler...

Further Reading