Sanitary Sewer Manhole Invert Elevations

I bought a Chris-Nik Pipe Mic last year, and inverts are very easy now. It doesn't collapse like you asked, but it keeps the level rod plumb, and I believe that my inverts are more accurate, and the pipe sizes are much easier.

They have an invert worksheet that you can put your company logo on, and it makes the calculations pretty straightforward. The price was around $200, but the easy of use, and the more accurate measurements are worth it, in my opinion.

Feel free to drop me a line tomorrow at the office if you have any questions. Contact info is on my website.

Good luck

a Pipe Mic might work, but seems a little pricey. I've used a digital, 4 foot level; lay it on the leaning rod and do the math.

I've also tried a disto laser and wasn't real happy. It didn't like bouncing off water....

The tool of choice may depend on how far the pipe is from the footprint of the manhole opening. For most applications I've had good results by duct-taping a framing square to the the rod -- being careful to align it -- in conjunction with a rod bubble. I've also used a carpenters inclinometer to measure rod slant, but that seems to be less accurate approach.

With a large number of manholes to dip, I think I'd spring for the pipe mic.

Pipe Mic makes it a piece of cake.

I have to agree on the pipe mic. I've helped Jimmy measure several inverts with his, and I feel a lot more confident with my measurements when I use it. It goes pretty quickly when there are two people there, too.

Thanks for chiming in Chris.

We were working on a design topo for a client earlier this spring, and the site had about 50 structures on it that we pulled inverts on. The pipe mic made it much easier. I would say that we pulled inverts on those structures in about six or seven hours.

The premade invert sheet really simplifies recording the data, and figuring the inverts and pipe sizes. I really like the 1 foot offset to keep the rod out of the poo, and the offset to the side allows the rod to stay plumb.

We have been doing a few of these recently too.

We made a footing for our staves. It looks a bit like the pipe-mic, but our one can not change the angle - its fixed at 45 degrees or so.

But we do have a pivot in ours so that the staff can be rotated to face the level while doing an invert. We've been using digital gear and we needed to be able to clearly read the staff for all pipes coming into a hole.

Using 1/2" pvc pipe I made a giant "L". I glued a 5' piece of pipe in a 90° elbow. Then I glued a 2' piece of pipe in the other socket. I also glued a cap on the open end of the pipe. Threaded couplings can be used to make the upright pipe longer for deeper manholes. We stuck the short end in the invert, marked the long pvc pipe where it hit the rim, or a straightedge laid across it, took the "L" out, laid it flat,and used a tape to measure the depth. You can use some sort of clamp to mark the pvc where it hits the rim. You could take measurements to the invert and top of the pipe to get the diameter. Plastic grocery bags can keep the pipe clean.
Not very fancy, but it works.

[sarcasm]be a man and climb down there with a tape[/sarcasm]

I'm sure you could just use a Standard fiberglass oval rod with a piece of rigid flat bar,maybe even have extensions on the flat bar, screwed into the bottom of the rod,a flat bar that doesn't flex easy,add the addition of the flat bar,use a level or rod bubble and you should be good to go.

We use the trig to resolve slope distances and grades all the time, it works for inverts too.

Go to the hardware store and buy a plumbers weighted pipe protractor for about $10 or $15. No batteries; they work on gravity.

Use 25' fiberglass rod to the invert, no matter how bad it leans, plumb bob string across the top, read the depth, read the slope of the rod in degrees, do the math back in the office when you are reducing your notes.

I have done this for the last 20 years with no problems. In a few cases where I could come back to check an invert without the severe slope (after the top was removed from the inlet) it was right on.

Give it a try - much easier that fumbling around with a right angle gizmo.

Ken

[sarcasm]Been a lot of talk on here, recently, about those eight foot ladders[/sarcasm]

Jimmy has some good points. Buy the Pipe Mic or equivilant if there is one. They can save you alot of time and headaches down the road. If you've blown a reading you know what kind of headache that is. I think they're only $200 or so, if you break that down per dip on this job and all the future jobs you use it on, it's not to much. I would hope you're making more profit than that on this job. We used to spend the time and money to rig something up and it worked fine. If your don't include you time in making it you'll save money. If you're times worth anything to you it'll actually cost you more making it. Now that I don't have some else paying me to make stuff on the fly, I'm a think about what I think about what I'm doing more.

For about $1200 (I might be wrong about the price) you can get one of these.
Lotta bucks but it looks slick. The Chris-Nik Pipe-Mic is a lot cheaper, and probably works better in water and sediment.

Thanks!

Thanks to all for your feedback - much appreciated!

Thanks!

Dual prism offset!

ftp://ftp.trimble.com/pub/to_sg/SC%20V10.80/Documentation/English/Help/Eng_SCDual_prism.htm

works great

we would drop a plumb bob down 3-4 feet from the rod sticking up out of the manhole, measure the offset to the sloping 25' rod, and calc the angle. then measure the slope distance and calc the the vertical distance. not a perfect method, but by using consistant measuring techniques (same side of 25' rod to measure from, etc), our inverts came out good. for inverts over 25', we have used as many as 8 sections of 4' range pole to measure down. make a good sketch to show your work as backup.

Thanks!

Back in the old days when it seemed I was dipping more manholes than surveying them in I devised a fool proof cheap method. It wasn't just the inverts that were important, so was the pipe size. Sometimes you never know if you had the flange or the pipe on the top. Much of those combined sewers were installed around the turn of the 20th century and there basically were no records. Just years people hooking whatever they needed to go away up to the closest pipe, with whatever pipe they had on hand.

I just took the oldest 25' level rod we had and simply duct taped the biggest 90 deg shelf bracket I could find (I think I found a 16") after I pounded the "working end" of it flat. Most manholes you could get pretty plumb, almost, but still better than leaning. And you knew you had the actual pipe and not the flange. I've even used flagging to attach a lath for bigger MH's.

And a really really good flash light, and a gallon of bleach for when you're done.

The pipe-mic works well, we've used them in the past. To verify pipe sizes we take an old rod (Old Stinky), spray a good bit of paint at about the height of the pipe diameter, and "scrub" it up against the top of the pipe (with the bottom in the invert), then you can lift the rod out and measure the pipe diameter. Have lots of disposable gloves and hand sanitizer. Another thing to keep in mind is the "routing" of the pipes, be sure and have the correct manholes connected.

Andy