Culvert Advice -- Plastic vs. Galvanized ?

[PineRidge]

Here's a picture of our culvert pipe just after I threw it in the ditch.

 

[PineRidge]

This is the fun that follows. Hand shoveling several tons of concrete dust mixed with 57s over the culvert pipe. Notice how the driver dumped the load on the road. /forums/images/graemlins/frown.gif

 

[OrangeRidge]

I went with a 20" concrete pipe . Has a lot of integral strength .

 

[hazcad]

Corrugated galvanized pipe is old school. It scours over time, fills with dirt and sand and can clog easy and eventually erodes. It also has a very high coefficient of friction and needs a steeper slope to flow properly which is not always possible depending on your pipe invert elevations and or topography.
Smooth lined plastic pipe does not corrode and has a very low coefficient of friction (like crap thru a goose) and does not require a steep pitch to flow correctly and can handle a higher flow rate.

 

[AGTtactical]

I used 18"x20' ADS/Hancor pipe (HDPE). Smooth on the inside. 18" is all you'll ever need. 18" was only $5 more a section than 15". Mine is buried at least a foot, and I've had 30 cubic yard dumpster trucks filled with wet soil drive up my lane two dozen times, and they didn't do a thing to the pipe. Truck and soil weighed about 80,000#. I only wish I'd have done 30' long, but the salesman talked me out of it, saying I never sell anything but 20' for a driveway". Yes, but if you want a nice gentle bank for mowing, a 30' would be vastly better. The deeper you go, the longer the pipe you need. The deep you go, the more weight you can carry.

 

[North West Farmer]

Great discussion! If you have beaver near your installation, plastic may be damaged by them. I was watching a YouTube channel the other day in which a pond drain had failed due to beavers chewing on the vertical inlet that maintained the pond level or depth of the water, in this case made from plastic corrugated pipe. I have beaver in our creeks and was considering replacing a 48" metal corrugated pipe with the plastic corrugated pipe, until I saw the YouTube video. I had not considered the possibility of beavers chewing on the pipe. In the video presentation, the beaver had completely destroyed the plastic corrugated pipe that needed to be replaced. Something that possibly should to be considered when deciding which type of pipe to use if the pipe will be exposed to beaver activity.

 

[nortonbyk]

You are correct about the galvanized pipe. My first 36-inch pipe beneath my driveway was a 40 foot corrugated galvanized pipe. It lasted 14 years before it completed rotted out along the bottom, then water flow undermined the soil, and then finally had a catastrophic failure during a heavy rain event which left me and my family stranded. There are well established civil engineering specifications for culvert pipe installations. My advice is to go with smoothbore, corrugated plastic, and backfill in compacted lifts. A 12-inch pipe may never need such a production, but mine did.

 

[pikewrench]

A lot depends on depth of cover over pipe, back fill material, and exposure to sun and possible damage of trailered vehicles running over exposed piping. Yes corrugated metal rusts but will not require a lot of backfill. Most plastics exposed to sunlight have the oils leached out and become brittle over time. Soft fill such as soil and sand that hold water will allow vehicle tires closer to the pipe and shift allowing the plastics to break and metal to egg. Fill of larger rocks will cause plastic to crack and fail when a load travels over them while metal will also dent and cave in. The HDPE (corrugated look on the outside and smooth on the inside) will last the longest provided it is bedded properly-what the county is using here to replace old culverts that cross the road

 

[nortonbyk]

You are right, pikewrench. There are backfill soil specs for the bottom third, the middle third, and the top cover. That is almost never done. Backfill for metal vs. plastic may be different. I'm not a civil engineer, but I have seen many a culvert replaced here in farm country.

 

[BarnieTrk]

Fellas,
What about the slope?
Is it better to provide drop (say 1/4" on 10') across the culvert or install it level and allow the open ditch to provide / deliver the slope to drain away the water?

Thanks for dredging up this discussion, Guys! :thumbsup:

BarnieTrk :dance1: