Water Supply Net Work

Almost surely less than in a metallic system. However, the pipe can bend or crush more easily (I think), so careful leveling (or consistent slight grades) should be maintained, along with adequate top cover. The interior is smooth, and the pipe is virtually noncorroding. Sand or gravel could abrade it, but they will abrade metal also. HDPE is easier than metal to form into gradual bends where needed. No problems with galvanic corrosion.

I don't know how well HDPE compares for shock loads, such as could happen from rapid closing of valves. Valves might need to be flanged, or attached by some sort of compression clamp. If so, they may be more expensive than threaded valves.

Those are just a few ideas into the picture, but with care to the specific needs of this type of piping, it should prove successful.

I'll just add two things to Tornado's post.

1. If welding is required, it takes some training and skill.

2. HDPE is more susceptible to rock penetration if not properly bedded.

OK, 3 things. Plastic is easier to repair, if necessary.

Ok, 4 things. Plastic is susceptible to ultraviolet degradation if exposed to sunlight.

I have an installation that is more than 20 years old using HDPE pipe for potable water system. The pipe crosses through various environments- espcially sensitive are a point where it crosses a surf line (from subsea section to land section- extreme mechanical stress) and several stretches where it is exposed to sunlight. There has not been a single failure in the system in the 20 years it has been functioning. We have a parallel system used for diesel fuel, exact same pipe, more than 20 years life, no failures. I know of no other piping system that can survive such abuse.

Some added thoughts- most people think of PVC when they think of plastic pipe. PVC would not last a year in the installation I suggested.

Connections (pumps and valves) are made by welding NPT nipples that have been factory-swaged to short sections of HDPE.

No special attention has been given to proper bedding of the HDPE pipe. No problem with rock penetration (not true for PVC). Note, this installation is also in an area subject to frequent small earthquakes- lots of ground shifting. Also, heavy rains/flooding. No physical damage has ever been experienced with this pipe.

We originally learned about the pipe from an oil well driller- they lay this pipe on the surface, drive heavy equipment over it, then reclaim it for service at the next drilling site.

HDPE is does not degrade in sunlight, as does PVC and other plastics.

The installation consists of a gravity feed (across a saltwater bay) to a pump station, from where the water is pumped up a 140 foot hill to storage tanks. From the storage tanks, water gravity feeds to the facilities at sea level (~70 psi- need pressure reducers for much of the system).

The original piping system was done in steel/copper back in the early 1960's. The steel pipe corroded from the outside after about 20 years of service due to highly acidic soil conditions. Original repairs were done with PVC, which did not last. Switching to HDPE eliminated all maintenance on the piping system.

Welding is required/recommended. It does require special equipment and training.

I have no connections whatsoever to manufacturers or vendors of HDPE pipe. I just like the stuff so much that I spec it for EVERYTHING, including underground electrical conduit...

HDPE does degrade in sunlight. However, they can add carbon black to extend the life expectancy, which also increases the cost.

Only thing I'd comment on is "Welding is required/recommended. It does require special equipment and training". Butt fusion needs operator training but socket fusion (heating wires embedded in the fitting) while more expensive, only needs common sense and following of instructions, and works very well.

Cheers..........Codey

the Online newsletter "Water World continuing education" ,might be a good resource as well .

Other posts before me spelled out quite a bit of the HDPE pipes limitations. I just wanted to add a few more concerns that haven't been addressed so far.

You must be concerned about widely fluctuating dynamic pressures, such as "Water Hammer", as it can split open the pipe. Additionally, if you have recurring differential pressure extremes to HDPE is susceptible to fatigue, much like aircraft aluminum fatigue...the corollary is similar.

Make sure if you are installing the pipe aboveground or on the ground exposed to Sunlight that it is certified as having been manufactured with a UV Stabilizer conforming to applicable ASTM Standards.

Also, it doesn't tolerate direct sunlight and the resulting higher material temperatures. Under these conditions, the material becomes softer (for a better layman's term) and therefore it's becomes more susceptible rupture once the temperature reaches a specific level. this level can differ from one manufacturer to the next as well differences in material grades. I don't know where you're located and if this is a real concern. I do know that in many countries all over the world I've witnessed some very dangerous practices being followed by water companies and communities where HDPE water main and service lateral pipes had been laid directly on the ground or in filthy water and puddles, a very dangerous situation in regard to health safety and water quality/contamination issues. Also, is the crushing issue of exposed pipe. It is much better to bury it at least 1 foot (more the better if run over by motor vehicles and trucks) below grade.

Assure that the HDPE is conforming to minimum requirements of applicable ASTM standards.

There are new snap and lock HDPE fittings and couplers now available on the market that virtually eliminate the need to fusion butt weld sections of HDPE pipe, except where you may have to perform an emergency repair where fusion welding of the plastic is a necessity. Repair sleeves of this type are also available. Be forewarned, all of this new technology is expensive, but not prohibited. Costs will eventually come down, hopefully.

One problem of HDPE is that in the manufacture of the plastic matrix, a whole lot of petroleum is used to make it, and as we all know the price of oil is going to spiral up and up, therefore costing your community more and more for repairs and expansion of the distribution system.

Frankly, as a water engineer I much prefer using Ductile Iron Pipe (when installed, protected, and maintained properly) over any other type of pipe material in a public water distribution system because of it's durability, strength, and superior resistance to dynamic conditions and rocks in the pipe trench. It's much like granite, the rock of ages.....you have a hard time breaking or killing it. Problem with it is it's initial cost. Great benefit is that it could possibly last 100 to maybe even 150 years into the future when cared for and maintained.

Lastly, don't purchase cheap pipe that doesn't meet the aforementioned requirements.

Good luck with your water system.

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Good answer CaptMoosie: You have obviously dealt with many pipe issues over time. While reading through the replies, yours seems most comprehensive, when read with the addition of the tracer wire and warning tapes.

We have also experienced pipe failures that were diagnosed as "fatigue cycle". These failures related more to the diurnal cycling of pressure in the system as reservoirs filled overnight and emptied during higher demand in the day.

The failures were typically highlighted by the pressure waves created by water hammer in the system. One specific manufacturer replaced a 12km section of 300mm pipe twice, but all other material in the network seems to be performing well at the moment. Age profile is from laid last month to 30 years old. [We have around 400km of pipe, mostly 150mm diameter but up to 300mm, all burried. Some in residential, some in bushland. The test of time has not yet been of sufficient duration for these items, but I suspect that in 100 years there will be significant confidence in these products.]

I do not share your preference for ductile iron (even concrete lined) as we have significant acid sulfate soils in this region. Yes, if wrapped properly then the anaerobic systems are succesful, but a single point failure becomes an issue. Though the strength of Ductile makes it the material of choice in some specific locations.

Keep up the good work.

Have any life cycle studies, (manufacturing, transport, environmental problems, concerns) with your Ductile Iron Pipe been done?

I wish you could see the result of your choice of material in 150 years time. I wish I could as well. I am so proud of you my supreme skipper . How about you have a piece of pizza?

From experience my choice would always be HDPE . Think of the saved man handling hours, carrying and detailing tools and methods that have to be implemented when any kind of iron is involved. Ductile Iron Pipe

I was up in the mountains a while back and while walking up a steep rocky creek which runs all year round, there was a 2" HDPE pipe sticking out of the boulders and gravel. It was possibly dislodged from a plantation in a lrge flood and was embalmed in large boulders. It must have gone through hell to get were it was now. It must have also been there for years because their was moss growing on parts of it. Us trying to remove it resulted in a wasp attack. Phillip smashed his camera in the process.

They had built a nest inside the pipe and they got us out of there quick smart but still stung. They should know were they built there nests and in or on what. I would.

Please zafferkhan think again and do a life cycle study or have it done. There could be free information out there. Oldies are not always Goldies and I'm old enough to know that.

Good luck, Ky.

Hey Ky, how's it going? To answer your question, yes, there have been life cycle studies completed by CIPRA (now DIPRA). I wish I had a copy of those studies here, but alas it is in the library of an Engineering Office I once worked for. For the most part it found if the DIP was asphaltic coated and double cement lined, properly poly-wrapped and the water properly treated as well to a 'neutral pH" (7) than the pipe could last quite a while. I think the projections reached out to 120 years. I personally think that assessment was a tad low if the proper longevity procedures are undertaken.

When I was a City Engineer nearly 20 years ago in an old small upstate NY mill city (pop. 23K at the time...max pop. was 54k in the early 1950's) my water department crews were routinely digging up old sections of Cast Iron Pipe (CIP) that burst due to extreme cold snaps (some winter nights down to -20F) and high pressures. these pipes had been installed back in the period between 1882 through 1889 when most of the city's 250 miles or so of water main, transmission mains, pumping stations, and 6 raw water reservoirs had been constructed. In some older sections of the city the CIP even dated back to 1848 when the first mills were built! Anyway, these removed sections of CIP looked practically new inside and out! I couldn't believes what I was seeing....just a thin coating of rust and barely anything else! The raw water from the watershed reservoirs was pretty close to pH=7, give or take, and was treated in the plant with Multi-Media rapid filtration with some coags added to precipitate suspended solids and aid in the filtering of the raw water, then finally chlorinated. It's amazing that these pipes survived as long as they did, especially having been pounded to death by the heavy tuck traffic on the state highways and the city streets which serviced the factories and mills! Most of those pipes had ages reaching back 113 years, whereas the pipes from the old sections of town were roughly 147 years old! BTW, I left that position in 1995.

As we all know DIP is much more durable than CIP of olden days, so I'm confident that it can have a significant length of service. I've seen a whole chit load of pipes in my tenure as a Civil Engineer (nearly 34 years in the biz) and I'm still sold on DIP. Granted that it's a bear to install and is more costly, but installation problems can be overcome by any good pipe Contractor that has superior equipment operators, well run equipment, above average pipe laying crews, and an efficient pipe laying operation. You're right, it's not as competitive as HDPE, but each type of pipe has it's own merits and detractors. I have seen crews laying DIP as well and as fast as any HDPE pipe crew could. Having the right equipment present on the project site to handle DIP efficiently overcomes, errrrr alleviates, a lot of back-breaking grief of manhandling pipe, so I don't see that it's so much an issue. Cost certainly is though, and HDPE wins hands down there!

I've used HDPE more and more for a whole bunch of different applications...mainly for sanitary force mains, large irrigation systems, and for storm sewerage lines and culverts, not water mains. It's interesting to note that the vast majority of incorporated municipalities (Villages, Towns and Cities) in New York State (and most New England and Mid-Atlantic States) only allow the installation of DIP in their water distribution systems. It wasn't uncommon 20-25 years ago that they had permitted the use of PVC AWWA C900 water main pipe, but with so much breakage and wear on that pipe they have gone back to using only DIP. Nothing else is allowed, and in fact, some munies are forced to replace the PVC mains as they're falling apart well before their intended life cycle of around 50+ years. Just too many probs! I think it may be too soon to truly estimate what the life cycle for HDPE pipe will be because the technology is still too young (infancy?) to make a sound judgement call yet.

Ta mate!

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HDPE pipes are preferred during recent years for water supply due its easy installation and maintenance. Use good quality as per the relevant international standards to avoid future breakdowns. I have notices in one of the completed water supply projects High pressure HDPE pipes were used and so far no problem has observed.

Hello Zafferkhan:

I have very limited use of HDPE on water systems but have used it on Landfill leachate collection systems. The landfill use in extreme environments was more than adequate. Even when the ground was settling, a common problem, the pipe stayed together. Fusion irons and welders are available for side connections and may be required. If you are laying the pipe use GPS mapping for future locating. You may want to lay a trace wire as a location backup. We have used HDPE on water supplies but only on the transport of the water from a well to a building (retirement homes, etc). Never have these installs been a problem. I also notice that the electricians are using HDPE (not PE or PVC) as electrical conduit for street lighting.

Go for it. Good Luck

Very good recommendations regarding the mapping of the pipeline with GPS equipment and backing that up with a tracer wire.....actually it is advisable to install a pair of tracing wires atop of the pipe or at least in the pipe zone backfill.

Also, it is best to install a continuous blue colored foil warning tape at no more than 18-inches below grade in case someone is excavation in the close vicinity or over the pipe trench they are then duly warned that a water main is buried directly below. Sort of like early warning! this foil tape can be picked up with standard man-potable magnetic locating equipment that is used in the water works field.

Once you have all of those GPS coordinates recorded make sure you complete the As-Built maps or Record Maps that will depict the exact location of the pipeline and all fittings and valves. It is not a bad idea to swing tie-off dimensions (a minimum of two required per coordinate point for triangularization) in the field from fixed know points that cannot be easily moved or disturbed. These field dimensions will serve as a vital backup to the GPS and also act as a verification of the GPS plots.

Have a nice evening!

You should be aware that HDPE is tested differently then steel or PVC for strength requirements. HDPE pipe rated for a specific pressure will be substantially weaker than steel pipe. It is all about the factor of safety they use and allow, since the differing materials are tested under programs established by different orignating organizations. substantial pressure variations may not make HDPE allowable.

RCE, a very good posting with equally important and valid points made regarding the various differences used in determining Maximum Allowable Sustained Water Pressures and related FS for different types of water pipe materials. I concur fully.

Each type of pipe material has it's proper place and utilization, based primarily on it's PROVEN and certified laboratory test performance characteristics as well as type of fluids and slurries it is to convey.

Again, actual field performance will usually be tied back directly to proper engineering design and installation during construction.

You get a GA from me.

You haven't mentioned much about your climate or topography etc., that perhaps could have some bearing on answers to the questions you ask. With regard to the various pipe materials mentioned in this thread however, all the basic material types of pipe available today (ductile iron, pvc, fiberglass, polyethylene etc.) have actually been around a long time e.g. from about the time of WWII, or shortly thereafter. It is my understanding specifically polyethylene material was reportedly invented in ~1933. I suspect at least the attempted application of this material to tubing and pipe applications probably followed shortly thereafter. Therefore, it has been around about as long or longer than e.g. ductile iron or pvc pipe. Many of the larger utilities in particular actually have experience with most or all these pipes somewhere in the systems they have built or acquired, over many decades.

However, for many reasons (and while the piping obviously has some utility, I suspect there are many) as graphically shown in most recent EPA reports e.g. Table 4 pg 25, Table 2 pg 12, and Table 1 pg 11 at http://www.epa.gov/nrmrl/pubs/600r09048/600r09048.pdf polyethylene has traditionally achieved little relative usage in the municipal water and wastewater markets of the USA. Some of the reasons, perhaps non-obvious to some, are explained in careful reading of direct head-to-head testing of pipes e.g. as shown in publications like at http://www.dipra.org/pdf/DIPvsHDPE.pdf and http://www.dipra.org/pdf/directServiceDIPvsPoly.pdf . Perhaps time and experience will reveal yet others.

On the DIPRA website you can also find a software with tools for designing and specifying Ductile Iron pipe.

http://www.dipra.org/programs/

hope this help

Vitt