Today I saw the town maintenance man repair the elbow in a 2" plastic
water pipe, two feet deep in sandy soil.
He said water pressure had separated the joint. His solution was a
steel stake on either side of the joint. That's what he had before, and
It seems to me that enough pressure to separate a joint could also, in
time, move a stake in wet, sandy soil. Is that the best way to brace an
The guys in my area use bags of premixed concrete for 8"
underground irrigation pipe. Pressure won't exceed 80 psi probably.
Most often it stays under 50.
They just put the bags in around the elbow. The pipe is 5' deep or
maybe a little more. It might work to put a partial bag around the
pipe you described. Tamping it in around the elbow would help.
A properly glued joint will easily withstand the force assoicated with
"normal / reasonable" flow levels in "small diameter" piping.
Unless the flows in this system in the 100's of gpm the elbow forces
will be small.
High flow rates and / or large diameter pipes can require a "thrust
block" but I seriously doubt a 2" line would need one or if it needed
one, that a "stake in sandy soil" would do the job.
Do oyu have any idea what the flow is?
I don't know the flow, but it feeds an office with one dentist 200 yards
up the road. Halfway, there's a tee that feeds an office across the
road. I don't recall seeing more than two cars there. Static pressure
is about 40 psi.
I wonder if suddenly shutting the water off might have broken the
Concreting completely around an elbow in 2" line with 40 psi static
pressure is totally unnecessary, the wrong solution here. Even if a
thrust block was required, completely encasing the fitting is frowned
If water hammer is a potential problem, better to mitigate with a
properly sized and installed water hammer arrestor than "brute forcing
it" with concrete.
Thrust blocks are generally not needed for piping below 4"...plus 40
psi static pressure is a pretty wimpy system.
My bet is on a bad glue joint.
That sounds right. Maybe he didn't reglue it because he couldn't get it
dry with water continually trickling out. (I wonder how a pro would
have reglued it.) Maybe he has seen a lot of glued joints break in this
town because a lot of underground joints were glued badly.
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