How to Read a Bubble Level for Slope

Welcome Newcomers Only registered users may post in our forums. Please register and join our community! OP enthusiast Joined: Aug 2006 Posts: 220 My father and I just put some corregated metal under our deck (two story house). This will allow us to sit under the deck when it's either too hot out or the weather is bad. We have allowed a drop of approximately 1/8" per foot (10 feet) for the water to drain, and the system is working well. It's difficult, though, to tell exactly how much drop because of uneven terrain. We put a level up and the slope is definitely going the right way (which we knew because the water is draining well), but we were wondering how you would read a level. Say, for instance, if the bubble is all the way out, half, 1/3, 1/4, etc., what kind of drop is that? Thanks! Frank Joined: Sep 2003 Posts: 8,552 Carpal Tunnel Carpal Tunnel Joined: Sep 2003 Posts: 8,552 Unfortunately, you can't really use a level to do that. Basically, a level is just too crude a tool to give you the slope of an angle. What you can do, however, is use the level to mark a HORIZONTAL plane. Then, measure down from each mark the required distance to establish a 1/8 inch per foot slope. That is, you can use a spirit level only to determine a horizontal accurately. Then you have to resort to manual measurements to establish a certain slope from that horizontal. So, you can't use the level even to confirm the slope you have is correct. Joined: Sep 2003 Posts: 8,552 Carpal Tunnel Carpal Tunnel Joined: Sep 2003 Posts: 8,552 I'm not wanting to speak for Ront; he's an accomplished tradesman and can speak for himself. However, I expect his method involves placing the level on the sloped drainage pipe, raising the lower end until the level reads horizontal and measuring the height needed to achieve that. The result, divided by four, is the slope in inches per foot. But, Ront, that's not using the LEVEL to determine the slope. That's using the level to determine the horizontal, and then using a MEASURING TAPE to determine slope. That's not the same thing as determining the slope directly from the level, which I think was the gist of the original post. So far as I know, it's not possible to do that. But, a king's ransom to the knight that can determine slope with good accuracy (within 10%, say) directly from a spirit level. I still say it cannot be done, but hope to be humbly eating those words. Joined: Jul 2003 Posts: 270 enthusiast enthusiast Joined: Jul 2003 Posts: 270 I used a 1" piece of foam (blue) taped to a 4' spirit level. this gave me 1/4" per foot drop for my grey and black water drin line and 28 years with no problem. I also have corrogated plastic under my deck to dry it in underneath. Put the spacer on top of level and it to will read level when you get the drop you desire and build up spacers to fit. Joined: Jan 2007 Posts: 7,010 Oldie Oldie Joined: Jan 2007 Posts: 7,010 I agree with Ront. This is exactly the way a level often is used. It is the best way to determine the thickness of a shim to make something level. We don't need to be deliberately obtuse, Tools and workmen work together in whatever combo gets the job done. You can't measure the slope by the position of the bubble. That's ridiculous. How do plumbers set the slope on a residential drainage line? They use a level. And 1/8 to the foot is about right. Too much slope sends the liquid waste flying and leaves the solids behind. contumacious but neither pusillanimous nor truculent Joined: Aug 2006 Posts: 1,253 veteran veteran Joined: Aug 2006 Posts: 1,253 Quote: I'm not wanting to speak for Ront; he's an accomplished tradesman and can speak for himself. However, I expect his method involves placing the level on the sloped drainage pipe, raising the lower end until the level reads horizontal and measuring the height needed to achieve that. The result, divided by four, is the slope in inches per foot. I'm not sure if he and I are on the same page, but he *might* be refering to levels with a built in second line. Two lines on each side of the bubble. When the bubble is at the second line, the pitch of whatever you are *leveling* is exactly 1/8" per foot. It's most commonly seen on torpedo levels but it may also be on some larger ones. I have several levels, but only the torpedo levels have the second line. He may have some that are longer AND have the second line. Just a guess. Al "Common sense is not so common."- Voltaire

How to Read a Bubble Level for Slope

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