On building a manometer

IaLeo

Well-known Member
Any experience or air handling experts here?

I want to build a manometer to look at the pressure differential between the room and the inside of the chimney.

I know about the loop of colored fluid that shows the pressure differences, but the metal tube that goes into the chimney pipe is the difficulty. Should it be 90 deg cut-off end and does it have to go in very far? Or does it have the tip bent down toward the upcoming draft....or maybe just cut off at an angle?

I realize that soot might compromise the reading eventually.

But I would find it interesting to see the effect various wind conditions would have on the draft.

I thank you for reading this far, friends and would appreciate your thoughts.

Leo (not law enforcement officer!)
 
It depends, I would think you want static pressure differential with no velocity effects, in that case you want the tube to have a
90 bend pointed, placed in the center of the flue and pointed towards the exhaust flow.

If that isn't possible you can likely get a good approximation with a straight tube that is 3-4 inches inside the flue.

Rich
 
A water tube manometer is not going to work for checking the draft in the chimney. You will not be able to see the 2 ends of the water move .02 inches apart in height.

Now, if you want to measure the gas pressure of the gas feeding the burner, you will be able to see about 3 inches of water column for natural gas, or 10 inches wc for propane.
 
The classic old Bacharach "Draftrite" uses a simple tube with a straight cut end. See link below.

As to building a manometer, the value you will be measuring is typically .05" of water, pretty tough to measure with a conventional U-tube manometer, typically, an "inclined manometer" would be used.

Also, be aware commercially-produced manometers sometimes use gauge fluids with different specific gravity than water, and won't give an accurate reading unless the correct fluid is used.

Here's an example from Dwyer:

<img src = "https://i.imgur.com/heFVCyj.jpg">
Classic draft meter
 
Wow...thanks everyone! I think I will back off and not be drilling holes in my stove pipe. I have no draft problems, so knowing me, I was ready to do something useless or compromising...lol.

Now to find the buried treasure reputed by the seller to be here the property...

Leo
 
Many years ago I bought a manometer to measure the
vacuum inside the chimney of oil furnace.
I hate working on oil.
I'm sure you could ask a local HVAC business to buy
one from their supplier.

Did you check amazon or ebay? That's the place I
would look. Or I would call my sister. She would have
her HVAC supplier drop ship one to my address.
 
We used to use magnehelic gauges to check air filter conditions, but I'm not sure if they're sensitive enough for a chimney. What Jim suggested is probably
better.
 
Leo,
I googled manometers on ebay. Many pages
electronic manometers. They even have
some old school ones.
geo
 

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