Until today I've been content to measure manhole inverts with an unadorned fiberglass rod, using a manhole hook laid across the open rim as the measurement point. For deeply recessed inverts I'd put a construction-grade clinometer on the rod to calculate the vertical distance. However, one of my current projects involves getting inverts on 30+ manholes, so I decided to spring for a Pipe-Mic.
The primary appeal is the vertical offset feature, which makes it easier to get a plumb measurement on the pipe invert. But that offset brings with it a good opportunity to bust a foot, since the direct rod reading at the rim is a foot too small. So I made a companion tool to allow the rod to be read directly.
It's just a 4-foot length of 1" square aluminum tubing, 4 pieces of aluminum strap, some bolts and wingnuts, and a few other bits to make storage a little easier.
(Those "extra" holes at labels A and B? They're the result of "measure once, drill twice" syndrome.)
The nylon rope is used to tether the device to something -- the truck, a hand cart (which I often use in urban settings), or even a belt loop -- to keep the tool from falling into a manhole accidentally. The top strap is 1 foot above the bottom of the tubing, so the rod is read at the top edge of the top strap.
All of the structural pieces fit inside the tubing for storage, and the hardware keeper is retained by a wire loop and a hitch pin. The rope just clips onto whatever's convenient.
I test-drove the whole setup this morning on 15 manholes, and am generally satisfied. I encountered one drain manhole with pipes set back too far to reach with the 2-foot Pipe-Mic arm, but I got close enough to plumb to eyeball an adjustment. The optional 3-foot arm would be useful for these, but wouldn't fit in some of the others I opened today. I'll probably not invest in it, and revert to prior methods for those large-diameter manholes if need be.
Jim,
It looks like your PipeMic can double as a pizza cutter!:-P
> It looks like your PipeMic can double as a pizza cutter!:-P
After what it cut through this morning, I'm not cutting any pizza with it.
> Until today I've been content to measure manhole inverts with an unadorned fiberglass rod, using a manhole hook laid across the open rim as the measurement point. For deeply recessed inverts I'd put a construction-grade clinometer on the rod to calculate the vertical distance.
I've been using the old level rod and slope indicator, read to a string, for years. When you do the math, a degree on the angle does not amount to much on the distance down.
Does the pipe-mic really make it easier? It looks like a hassle to cart around.
Having asked that, your 1 foot offset gizmo is rather slick!
Ken
Yes, I have been using one for a few years, and I hate measuring inverts without one.
I use the invert worksheet that is available on the ChrisNik website. It is pretty slick, and makes the one foot bust pretty hard, in my opinion, but I am very used to it, and ALWAYS use the 1 foot offset, so I am used to adding it to ALL my measurements.
I am, however, trying to visualize Jim's invention. It looks pretty slick.
:good:
:-X
> Does the pipe-mic really make it easier? It looks like a hassle to cart around.
The Pipe-Mic is bulky, but not enough to make toting it any harder than carrying a plain rod. And it weighs so little that when the package arrived I thought the box was empty!
The places I found it especially helpful were at drain manholes that have DI runs entering high on the wall, making the off-plumb angle to the rim pretty big. Being able to set the wheel on the invert and still maintain a plumb rod was nice.
A couple of other notes:
1. A bullseye bubble on the rod is advisable if you're trying to bear down on the errors. Because of the offset contact point you can't plumb by feel, so it's easy to start picking up hundredths if you're eyeballing plumb.
2. With a 2-foot arm properly attached, I estimate that there's about 0.03 foot of slop in the device due to the play in the attachment pins. Invert depth also introduces some uncertainty, as it's harder to judge the amount of loading on the arm. With a 3-foot arm I'd expect that error to be a bit larger due to increased flex.
3. Today I was working solo on a college campus where truck access is limited, so I was using my Fold-It cart (a collapsible aluminum garden cart). In it I had 3 each 36" traffic cones, a 6-lb. sledgehammer for burping lids, a manhole hook, the Pipe-Mic and the home-made rim boot device. (I had intended to bring a garden sprayer loaded with a water-bleach mixture, but forgot when I left the office.) When measuring inverts solo it always seems like you're short at least one hand, but using the Pipe-Mic didn't make the situation any worse. I got through 15 manholes and the only thing I dropped into one was a concrete nail that fell out of my vest, so I consider that a success.
4. As a P.S. to the dropped nail, for some years now I've been in the habit of putting my truck keys in the top right pocket of my vest because I use them so often fetching things from the truck. But after having a padlock key fall into a DI awhile ago (fortunately I had a spare), I've taken to clipping a Key-Bak retractable keychain gizmo to my vest and clipping my truck keys to it. Were it not for that, today's concrete nail would be accompanied in that sewer manhole by my truck keys.
I just picked up one of those Pipe-Mics off of eBay for $50. That deal was too good to turn down, but it appears to be one of the older models that does not have the 2 notches for the protruding screws on the newer Crain rods. It has a note written in Sharpie that the offset is 0.95 from the top of the screws. I wonder if I could just grind a couple of notches.
> I just picked up one of those Pipe-Mics off of eBay for $50. That deal was too good to turn down, but it appears to be one of the older models that does not have the 2 notches for the protruding screws on the newer Crain rods. It has a note written in Sharpie that the offset is 0.95 from the top of the screws. I wonder if I could just grind a couple of notches.
Adding your own notches would be an easy fix, though I suggest using a chain saw file rather than a grinder -- you'll have much better control over the notch depth, which will determine index accuracy. The device is made of aluminum, which is pretty soft even when hardened, and I don't believe the Pipe-Mic is.
> Adding your own notches would be an easy fix, though I suggest using a chain saw file rather than a grinder -- you'll have much better control over the notch depth, which will determine index accuracy. The device is made of aluminum, which is pretty soft even when hardened, and I don't believe the Pipe-Mic is.
Thanks for idea. Can you tell me how deep the notches are?
When my crews use the pipe-mic, I have them write what they read, then add "+1.0'" to their notes.
i.e.:
STMH #1150
FL=5.50'+1.0'
5.30'+1.0'
This way, the office knows that the pipe-mic was used and there should be no question whether the crew added the offset or not.
My tech then created an excel worksheet were we enter the following info:
pt no. of the manhole, direction of pipe, type of pipe, rim elev, fl invert, top pipe invert
The worksheet then calcs the pipe diameter in one column, displays the FL elevation in another, and displays all info in a single column so that we can copy and paste the info into acad or microstation.
example:
RIM ELEV = 859.88
FL NW 6IN PVC = 853.53
FL E 6IN PVC = 853.53
FL S 6IN PVC = 853.43
It is a pretty slick worksheet.
Miguel A. Escobar, LSLS, RPLS
Manholes / Pipe-Mic (SOLD)
> > Does the pipe-mic really make it easier? It looks like a hassle to cart around.
>
> The Pipe-Mic is bulky, but not enough to make toting it any harder than carrying a plain rod. And it weighs so little that when the package arrived I thought the box was empty!
>
> The places I found it especially helpful were at drain manholes that have DI runs entering high on the wall, making the off-plumb angle to the rim pretty big. Being able to set the wheel on the invert and still maintain a plumb rod was nice.
>
> A couple of other notes:
>
> 1. A bullseye bubble on the rod is advisable if you're trying to bear down on the errors. Because of the offset contact point you can't plumb by feel, so it's easy to start picking up hundredths if you're eyeballing plumb.
>
> 2. With a 2-foot arm properly attached, I estimate that there's about 0.03 foot of slop in the device due to the play in the attachment pins. Invert depth also introduces some uncertainty, as it's harder to judge the amount of loading on the arm. With a 3-foot arm I'd expect that error to be a bit larger due to increased flex.
>
> 3. Today I was working solo on a college campus where truck access is limited, so I was using my Fold-It cart (a collapsible aluminum garden cart). In it I had 3 each 36" traffic cones, a 6-lb. sledgehammer for burping lids, a manhole hook, the Pipe-Mic and the home-made rim boot device. (I had intended to bring a garden sprayer loaded with a water-bleach mixture, but forgot when I left the office.) When measuring inverts solo it always seems like you're short at least one hand, but using the Pipe-Mic didn't make the situation any worse. I got through 15 manholes and the only thing I dropped into one was a concrete nail that fell out of my vest, so I consider that a success.
>
> 4. As a P.S. to the dropped nail, for some years now I've been in the habit of putting my truck keys in the top right pocket of my vest because I use them so often fetching things from the truck. But after having a padlock key fall into a DI awhile ago (fortunately I had a spare), I've taken to clipping a Key-Bak retractable keychain gizmo to my vest and clipping my truck keys to it. Were it not for that, today's concrete nail would be accompanied in that sewer manhole by my truck keys.
Thanks very much for the reviews (and Jimmy too).
This is now on my wish list, I will be getting the 3' arm too, what the hell?
As I tell my wife, it is not really money, just numbers on paper.
"Does the pipe-mic really make it easier?"
Yes!!
Bow Tie,
I just measured mine, and they are 0.28" tall x 0.30" wide, as per my dial calipers.
I hope that helps. I was going to take a picture, but the glare was too bad.
Jimmy
I have used the pipe mic on a lot of manholes. Works well until you drop it in a wet well and have to go fishin. I wish they would make a level rod with a built in laser at the bottom so you could just drop the rod, hold plumb, line the laser on what you are measuring and read. Offset manholes are tough to measure with the pipe mic. Overall great tool.
I was just thinking of asking you guys about this yesterday as I was dipping manholes. I was trying to think of some kind of invention that would allow me to measure recessed inverts and get pipe sizes. I kind of have to guesstimate now with just my level rod and a lath across the top, and I'd rather be more accurate. However, I think $225 is a little steep and I'm not sure about lugging a bunch of poopy aluminum pizza cutter parts around.
I've never though of the clinometer approach. Where can I buy a decent one, and how much do they cost? If the price is the same I'd rather have the Pipe-Mic I think.
Sunnto cost about $140 or you can make one:-P from a $1 store items
I didn't have calipers handy, but mine look about like 5/16".
A sturdier version of the same concept is the Empire 'Magnetic Polycast Protractor,' about $10 at your local hardware store. A link:
I have been using mine since the mid-90s. It works!
Ken
This was the first thing I thought of is build one like that, but then I thought of the humiliation if another surveyor or someone from a competing company saw me using it. I know you don't need something super precise to get an accurate depth at 10-20 feet or whatever... and I would worry about dropping that expensive clinometer to the murky depths. I kind of like that Empire one - it says reads within 1 degree which should be plenty good to get the required accuracy.