whenever i see manholes i always think they are too small for anyone to enter but i know people are supposed to be able to gain entry. what are the size guidelines required of people to get a job that requires manhole entry?
I’d think anybody under 250+ lbs could get in pretty easily. They’re not supposed to be cozy, it’s just an access point.
The smallest manhole size I’m finding purely through a cursory search is 1000mm (which I assume is diameter since it says width), or about 33 and 1/3 inches… Even when I was 195 pounds my waist size never exceeded 36 inches (granted I do have a slightly smaller than average frame). I’d imagine that anyone who isn’t about, oh, let’s go with Snarky Kong’s 250+ pounds could fit, though it would probably get rather tight near the upper ends of that (230+ probably). And note that was the absolute smallest I saw, I’d imagine a lot of cities use the 1200mm/47in or 1500mm/59in sizes I also saw.
They range in size (the manhole covers as well as the people) from 24" diameter (61 cm) on up to, say, 48" diameter (122 cm). Generally, the manholes underneath flare out some. The covers are the small part because there’s no call to put a bigger hole in the pavement than necessary.
No point, though, in a manhole too small for workers to get into.
The smaller manhole covers would be used for shallow manholes, such as those as for ‘catch basins’, the drainage boxes you can see in curb areas.
1000 mm = 39.37 inches. So the circumference would be 123.68 inches. That’s a pretty hefty waist/shoulder size!
What amazes me are the WWII newsreels, where sailors are going down hatches that seem impossibly small. During/after the attack on Pearl Harbor, some sailors escaped through portholes. (Granted, many who did lost some skin.) It’s amazing what people can get through if they have to.
I currently weigh ca. 310. I’ve never seen a manhole that looked like it would have been a particularly tight squeeze.
Wait, what? 
I had a friend in grad school whose weight tended toward 400, and he might have had some trouble with the smaller ones.
Witness a baby being born - yes, the skull deforms, but the shoulders don’t and they fit through.
Only if I get to film it, have props, and can add special effects.
And remember - waist size is roughly circumference, not diameter. A 33" diameter manhole would fit a waistline approaching 103". Granted, perfectly circular waistlines are only found in Weebles, but that’s still one big maintenance worker.
:smack:
Right, I forgot waist sizes are circumference (i’m not sure what I thought they were, clearly not diameter, secret forbidden magic I guess). Yeah, that broadens things up even more than I thought.
As other have mentioned they vary in size. Many of them don’t have enough room below from someone to fit in in the first place its only an access where the guys work can from the top.
I’m a big guy 6’1" 250lbs. I regularly go into manholes. I’ve only once had an issue where I could not physical fit into one. It was access to an under basement cistern system. It was never intended for people to go through. The access was not wide enough for my shoulders to pass. We simply enlisted child labor, smallish 14y old son of a friend.
Most commonly for me is working in well pits. Most of them are 6ft deep and 3 feet in diameter. Some have a full size cement cover others have a manhole cover. You get very skilled at learning how to position in odd ways to be able to spin wrenched as needed.
Or too small for equipment. The ones used for electrical & communications in particular, frequently have equipment underground. You need to be able to get replacements or added hardware through that access hole, too.
Well, with sufficient lube and lots of patience, all but the… Oh, I see. Never mind.
ISTR, when we had a design project for a prison once, that no opening leaving the prison could be larger than a certain diameter - I think it was 10 inches. Supposedly, a normal sized-man could escape through an 18" hole. Remember that move where the guy escaped through the sewer pipe?
True, but you rarely see maintenance workers entering manholes head first.
Check out google image search results for “cu chi tunnels”. People can squeeze into surprisingly small holes.
Do manholes nowadays have built in rungs to climb in and out? Back in the early '70s I was on a survey party and every once in a while we would have a job that required going into one. We had to use a ladder which narrowed the opening considerably, meaning I didn’t have to go underground because I was, and am, pretty rotund.
Yes, manholes generally have epoxy-coated steel ladder rungs in them.
Manholes are also considered to be “confined-space” areas, so in accordance with OSHA regulations, workers have to have a harness and retrieval device, continuous atmospheric monitoring, and a portable ventilation system.
But they exit head first.
What goes down must come up.
However, maintenance workers’ bones tend to be less smushable than a baby’s.