!!!! Thrust Block Your Valves Or Ending Water Stubs...

Little

Important important important. About 3 months ago, on a job we are doin, prolly $3 mil in work for us. A local utility company underbid us to get the water installation of this retail center. They were doin a decent job until they started busting up all of our curbs and then not providing sufficient cover over the pipe. Well, they had maybe 6- 6" Fire line stubs to buidlings, ending with a valve. Now, they had to pressure test the entire system and let it sit for awhile.

One morning i come in and start heading around the job doin my usual check, when i see a geyser of water shooting outta the ground, "HOLY ****!!" The pressure on the system caused the 6"valve to blow off and it do some considerable damage. It Undermined the entire corner of the footing of the building and wiped out i'd say 200lf of 10ft high retaining wall. The ramp into the detention basin was filled 4 feet high with silt, a total mess.

The cause, well first, it has been concluded that the mega-lug retainer glands were installed improperly, they used an pneumatic impact gun to install all the water line retainers and i guess the laborer had the gun on reverse and yes the megalugs snapped but the wrong way, away from the pipe. 2nd, no use of any thrust blocks at the ends of stub outs.

Sorry for the long story, USE THRUST BLOCKS!!

Double-A

Thrust blocks are all important. We went back and had to redo all the water lines in a new complex of 400 units because there were no thrust blocks anywhere.

I like those kinds of jobs. You just bid what it takes, show your insurance and watch them cry. They have little to no choice in who can do the work simply because of the insurance, equipment and experience needed.

I bet that poor utility installer's insurance rates just doubled.

For those of you that don't do big pipe, thrust blocks are large prefab or poured blocks used as dead weight to keep pipes from pushing themselves apart at terminations and turns.

__________________
"My clients’ wishes are the center of my attention." -- David Guido, a contractor in Woodstock, N.Y.
New York Times, July 20, 2006

Little

Same job, one of my guys was in the hole tying in a 4" line to the building, and has he is installing the stub and 45 out of the valve, i see the valve move, i'm like did that just move?? Again, wiggle wiggle, "Get outta the hole now!!" That right there was the second blow to the utility companies case, another bad install, their insurance guy just stood this with his jaw to the floor, case dismissed, he said right there to the owner that they would have to pay for the $500,000+ in damages.

Double-A

I can forgive much, but not endangering the lives of others with crappy work. I hope someone decides to press negligence charges as well. These folks are not fit to do this type of work safely.

__________________
"My clients’ wishes are the center of my attention." -- David Guido, a contractor in Woodstock, N.Y.
New York Times, July 20, 2006

mdshunk

Maybe I know a guy that bonked a 2" Victaulic elbow with a scissors lift and created a gusher. I can only imagine what a 6" like would look like going full bore.

dayexco

on the mega lugs we use, you can take out the bolts to remove the plastic spacer washers. that way you can use them on either d.i. or ips sized pipe.

__________________
someday, i'll be as patient as Nick.

Gmads

Around here, most valves come off the main with a flange to flange connection. Thus, connecting to stubouts are usually a simple matter. It seems like an odd design to call out valves at the end of stubouts for a future tie-in. Of course it REALLY doesn't help if your not going to properly install your fittings.

dayexco

gmads, we use the same type of sleeve/valve you're talking about when we are hot tapping the main. i can see for the cost differential on a new install that they didn't go that route. but it is unusual that the engineer on the job in the thread didn't spec the valve be located very close to the tee, and that the valve be thrust rodded back to the tee.

__________________
someday, i'll be as patient as Nick.

Gmads

I don't think cost is the issue. The difference between a MJ x MJ tee/MJ x MJ valve versus a MJ x FL tee/FL X MJ valve is almost nothing. The real issue is a sometimes lack of field experience in a design engineer. Somethings that are drawn up on paper aren't the best designs out in the field. I once had a set of drawings that showed a valve between two vertical 45 degree bends .

PipeGuy

I'd be interested in hearing if the failure occurred during the test period or subsequent to such.
Plain and simple, that's just an unqualified contractor doing the work; no different than me going out and trying to install an electrical service entrance without sufficient knowledge and experience.
We take it upon ourselves to restrain all valves within a zone of 250 x the pipe diameter (i.e., 250 x 8" diameter = 167') of a 'dead end' blocking and within which zone no other blocking otherwise provides thrust restraint to the valve. The additional cost of buying a swivel tee in lieu of a standard tee or some eye-bolts and tie-rod or a couple of mega-lugs is far less than that of some knucklehead coming along and getting hurt (or damaging property) because he didn't know better than to work in front of an unrestrained valve.

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Fortunately I keep my feathers numbered for...for just such an emergency. -Foghorn Leghorn

Little

When we are installing water of any size, we always rod the valve back to the tee or main. I always rod back my bends as well, i mean i could get away with no thrust block or rods 9 times outta 10 with no inspector there watching, but in the end you know something bad is gonna happen so i never take that chance.

TMatt142

You are absolutely right Little.....I was always taught "better safe than sorry" If I am installing watermain I never walk away from the project without using threaded rod on bends or thrust blocks. Tees, bends, any valve, hydrants, all need either thrust blocks or rod. The only bends I wouldn't thrust block are verticle ones with a lot of ground cover. Besides, they're relatively cheap ( 1 yrd pours 3 or 4 thrust blocks).

mtzia29

i have never wanted to or never will "cut corners" for the sake of time or money. Safety is our utmost importance. knowin that someone,someday will dig that up i keep that in mind! thrust blocks and all thread are common in this par of the country, no matter what job, even though we cuss'em!! Damn knuckel busters

PipeGuy

A pressure of 75 PSI puts 2120 pounds of force on a surface 6" round. It doesn't matter if a vertical bend is buried 30 feet deep - the physical properties of soil are NOT sufficient to properly block water main fittings.

__________________
Fortunately I keep my feathers numbered for...for just such an emergency. -Foghorn Leghorn

TMatt142

hmmm point taken.....still, MnDot specs never call for vertical blocks, in fact, it's never been discussed. Funny it's that way when you think about it but none have failed since they all have mega-lugs. Now, one factor may be the amount of water pressure usually run up in MN. Very low compared to ST.Louis where I'm at now. Mn usually runs under 100 where Mo water pressure is well over 100. Thus we use vertical thrust blocks down here...and....water main is very shallow here compared to MN where it's below frost levels.....8ft and deeper.