Potable water pipe connections 5

[iainuts]

I've volunteered to work on a small, water distribution project in the Dominican Republic which will benefit the local community. One of the first goals is to install roughly 3000 feet of 4" pipe from a well to an open tank. Maximum pressure expected is only about 70 psi. The pipe will be steel, ductile iron is being proposed. I suspect galvanized steel or black iron may be considered as well. The pipe will be buried.

I'm very familiar with welded, flanged and other forms of pipe construction but I'm being told there's another, more simple method that might use some sort of mechanical joint similar to a Fernco coupling, but I gather these Fernco couplings are only intended for low pressure lines (less than 5 psi).

https://www.fernco.com/

Unfortunately, the dozen or so engineers who have volunteered for this work are not piping experts and my background is primarily industrial piping and I've never heard of anything like this kind of piping connection system.

Is there any other method of connecting steel piping for use at up to ~ 100 psi?

If there is no easy way to connect lengths of pipe, would PVC be a suitable solution?

 

[racookpe1978]

Frankly, in the DR, you might get away with a "portable" (manually mobile) pipe system. In Hatii and in many other countries, if it can be lifted by one or two men, it will be lifted by one or two men, and be stolen quickly.

You will likely not be able to find acceptable (forget qualified) welders to keep the pipes sanitary. Threaded connections with a few unions to make up the joints is likely the best bet. PLastic and its glued joints? Maybe - but I don't know how easily a 4 inch diameter long run of pipe will stand up.

Height difference from end to end? Any hills or slopes in the middle?

 

[iainuts]

About half the elevation is the well itself. Once out of the well, the pipe will be buried under or alongside a dirt road bed, mostly flat. Total elevation is roughly 150 feet so only about a 75 foot rise over the 3000 foot distance. No significant hills.

Not sure about skilled labor yet. I suspect it won't be there so I feel there's a potential we end up going with PVC.

I wouldn't dismiss the idea of screwed fittings but this is fairly large diameter pipe for screwed fittings and it would also take some skill and effort to make the threads and rotate a 200 pound pipe.

 

[LittleInch]

If you're at that sort of pressure and don't want ot weld or screw, then these guys are your best bet -

http://www.vikingjohnson.com/en/category/dedicated

Call them to discuss the best and cheapest option if you want to go that way.

Some of these are end loading capable, but others may need thrust blocks.

At $" or 100mm for PE pipe, you can usually get long lengths ( 180+ m) reeled which means you only have a few joints to worry about.

PE is very flexible and forgiving long term to being dropped into a rocky trench.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[iainuts]

Thanks LittleInch. The Viking Johnson looks very much like what I was looking for.

 

[iainuts]

I stumbled across some info from Mueller and Dresser. Does anyone have any experience with them good or bad?

http://www.google.com/url?sa=t&rct=...ip_YaS_6nMAhWKKCYKHfosBGQQFggqMAI&url=http://

http://www.muellercompany.com/files...5PnhkvmMqroCXWgdzyzBtA&bvm=bv.119745492,d.cWw

http://ameind.com/expresseng/img/files/DRESSER_PIPE_REPAIR_PRODUCTS2.pdf

 

[btrueblood]

Victualic makes similar products also.

 

[bimr]

Municipal water piping generally uses flexible joints. That would be the bell and spigot joint.

http://www.pipingguide.net/2013/02/joingin-ductile-or-cast-iron-pipe-part-1.html

Restrained fittings are used at changes of direction. Thrust blocks are an outdated design and should not be used.

PVC pipe is another option. PVC pipe is assembled in the same fashion with bell and spigot joints.

 

[zdas04]

When I'm looking at a project like this, my main consideration is always "how long will it last?", the "how much expertise is required to install it?" and finally "how much will it cost?". The products I look at are:
[ul]
[li]Steel: Subject to internal and external corrosion. Expensive to install (both open ditch and intervention every joint). Considerable expertise is required to successfully install it. Life around 20 years.[/li]
[li]HDPE: Not subject to most corrosion modalites, pressure rating adequate for this task, 4" doesn't come in spools so it is stick built. I've done a couple of post appraisals on jointed HDPE projects recently and in both cases, the labor costs and re-work costs were more than twice budgeted amounts. This stuff is pretty difficult to install properly and you need an open ditch. Life around 30 years[/li]
[li]PVC: Pretty brittle and quite expensive in 4-inch size. Requires an open ditch and pretty gentle handling. Life around 5 years[/li]
[li]FRP (fiber reinforced plastic): Seems to solve all of the problems of the other products. You can do your entire job with one spool, you can install it with the plow people use for installing underground power service (lowest disruption and ditching expertise needed). I would look at Soluforce and Fiberspar and see how their Class 150 products stack up against the alternatives. I haven't run anything 6-inch or smaller in any other material for the last couple of decades. Life around 50 years[/li]
[/ul]

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[LittleInch]

Dave,

In most cases here I would agree with you, but the OP is talking about ductile Iron. There are millions of miles of ductile Iron pipe used in the water supply industry which last a lot longer than 20 years.

Also I usually reckon on max size of PE which can be reeled in long lengths as 180mm OD. So 4" approx. should be available on a reel. This means you can install it like a plough.

I don't think the Dominican Republic is going to import what is probably the best technological solution for a small water project though....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[zdas04]

I have worked in countries like the DR and the biggest issue I've found is long-term attention span. Rectifiers for cathodic protection get well maintained for several months and then (since there were no leaks in the first 6 months) they decide to stop monitoring them. Not bad people, just people who see the acute problems as far more important than preventing some future leak in 5 or 10 years. With a far better alternative easily available, helping to shift their focus to pipe that doesn't need much ongoing maintenance should be our goal.

I've seen HDPE SDR 13.5 in 4-inch spools, but limited to 766 ft. Nothing thinner.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[cvg]

Your pressure is only about 40 psi.
victaulic and dresser are not recommended below grade
Fernco is not recommended at all
threaded and flanged not recommended below grade
welded, no skilled labor to do it
glued pvc or bell and spigot are easy.
fused PE pipe requires skilled labor and equipment, but there would only be a few joints

schedule 40 pvc can use glued joints
AWWA C900 pvc uses bell and spigot joints
both are easy to joint but the bedding and compaction requirements are strict. installed properly, the life of buried pvc should be way more than 5 years.

ductile iron bell and spigot is also easy to assemble, although a lot heavier to lift. bedding and compaction requirements are much less strict for ductile. life should approach 100-years

PE pipe (drisco) can be assembled with minimal joints, bedding and compaction is not terribly difficult, but you will probably want to fuse the joints. there should not be many joints. buried would have a good lifetime, above ground would be susceptible to vandalism and damage.

i would stay away from galvanized steel or black iron - totally unsuitable for your particular application.

cement mortar lined and coated steel pipe would be good if the corrosion potential is low, however this takes considerable expertise to install and is very heavy. properly done would last easily 50 years. I am not convinced you could source this in the DR.

 

[iainuts]

btrue, thanks for the lead. I've looked for the Victaulic info, haven't located yet. Maybe tonight...

~

bimr, interesting about the blocks. The discussion so far has been to use them. No mention of "restrained fittings" - can you explain what you mean by that?

~

zdas, thanks for the info. The longevity of the system is obviously important as is low maintenance. Do you have links to any studies that compare longevity? That would be very helpful in convincing others on the team the best direction to go.

Dropping a spool of HDPE or FRP sounds perfect but I have to believe the spool is going to be enormous and require a specialized truck to haul it and lay it. That said, I'll certainly follow up on all leads.

Regarding cathodic protection, I take it that's required for steel pipe. Any additional leads on that would be appreciated. As mentioned, my piping expertise is generally high pressure industry piping, not potable water nor underground so I'm groping a bit for what might be important here as well.


Thanks again for all the input.
Dave.

 

[cvg]

you need to determine if cathodic protection is required. that requires specialized testing. if you do it also requires specialized installation requirements as well as long term maintenance. definitely not recommended for DR. better to stay away from steel.

 

[zdas04]

FRP has only been around for 30 years or so. Far too short a time for anyone to have determined the longevity. The first gen FRP I laid in the lat '90's is still going strong, but that isn't very long ago. The spools are designed to not be a wide load or an overly high load over the road. The Soluforce product uses arimid fibers (looks like hemp rope) for the strength layer and weigh's next to nothing. Fiberspar uses a glass reinforced fiber strength layer and it is a bit heavier. I laid a spool of 4-inch by sticking a pipe through the middle of the spool and laying it off of a rubber-tired hoe.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[MikeHalloran]

Victaulic couplings require machining or rolling a groove in the OD of the pipe at each end.
Internally ribbed features in the couplings engage the grooves to provide restraint.
It is therefore a 'restrained coupling', in that it is very difficult to separate with axial force once assembled.
There is a rubber seal adjacent/inboard of the groove.
In the DR, I'd worry about scratching of the pipe surface and contamination with dirt making the seal leak, and also availability of the tooling and skill for prepping the pipe ends.
Victaulic stuff is popular in sprinkler piping.

A Dresser coupling is vaguely similar to a Victaulic, except that it's much, much lighter duty and requires no special end prep of the pipe.
The axial restraint is provided by a thin metal toothed sleeve, over the rubber seal, that bites into the pipe OD.
The axial restraint is _optional_; not all Dresser couplings have it, so not all are 'restrained', and even the restrained ones are not in the same class with the Victaulic.

I wouldn't use either one underground, not least because they both use a small number of tangential bolts to secure the joint. Unlike pipe flanges, corrosion/ failure of any one of the bolts would compromise the joint's integrity.







Mike Halloran
Pembroke Pines, FL, USA

 

[77JQX]

What are the native soils like? Labor? Equipment? If soils aren't rocky, or you can keep rocks from direct contact with the pipe, my vote is bell and spigot PVC. I think that's a feasible material for a mostly hand installed low skill labor market - individual sticks can be moved by hand. The water system I work for has 100s of miles of bell and spigot PVC installed - life is way more than 5 years. I think glued PVC joints will give you more trouble, especially if compaction isn't as tightly controlled. Bell and spigot tends to be more forgiving under differential settlement. But you'll need to pay attention to joint restraint if you use bell and spigot pipe. I wouldn't rule out using thrust blocks - they've been successfully used for decades in the U.S., even though they're falling out of favor.

I'd stay away from ferrous materials - more corrosion prone, heavier, harder to install. Likewise, fusing HDPE takes experience to be successful.

I have no experience with FRP, but I generally respect zdas04's opinion. That might be worth checking out.

 

[zdas04]

The company I worked for before my retirement negotiated with a remote community to build a water system in return for letting us build a road through the edge of the community. We used bell and spigot PVC that was laid by crews who had been working on Centron FRP (fiber-reinforced plastic, AKA "fiberglass") so they were really sensitive to keeping rocks away from the pipe. Even with that we started seeing leaks in the pipe at about 4.5 years and the leaks were 1/month by year 7 when we took the system out of service and brought in a municipal water supplier to replace the well. The problems seemed to be rocks rubbing against the pipe, but no one knows where the rocks were coming from (kind of like when I was a kid on the farm and every spring we would have remove yet another 4-5 tons of rock from the fields before we could start planting). That experience made me very nervous about burying PVC even though I know that it is done all the time.

I have never been to the DR, and I know that every island is a unique ecosystem, I have worked on other Caribbean Islands and all the digging was either in volcanic soil or coral, either one would be quite abrasive.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[bimr]

Because buried piping such as a water line is fully laterally supported, the joints should be flexible to accommodate minor settlement; hence, less expensive joints, better suited for burial than bolted flanged joints, should be used.

For buried service, sliding couplings need not be harnessed if there is a sufficient length of pipe on both sides for soil friction to resist the thrust.

For ductile iron pipe, push-on and mechanical joints are the most commonly used for buried service. These joints allow for some pipe deflection (about to 5 degrees depending on pipe size) without sacrificing watertightness. Except in certain unstable soil buried joints are not required to support the weight of the pipe.

Restrained joints such as a bolted flange are not used underground unless needed to restrain thrust at a change in direction.

It is extremely rare in the municipal business to provide cathodic protection on a pipe.

Ductile iron is installed in a plastic bag. Ductile iron and PVC will have a service life of 50-100 years when installed properly and buried.

http://www.mrwa.com/WaterWorksMnl/Chapter 21 Distribution System Operation.pdf

 

[iainuts]

Lots of great advice, thank you.