Sunday, December 5, 2010

Pio V. Corpus WATER SYSTEM PROBLEM & RAM PUMPS

I received a comment on my previous blog post, ‘My Hometown Pio V. Corpus: POLITICS GONE WRONG’. The comment writer, presumably, is a fellow citizen in my hometown Pio V. Corpus, a kababayan. He calls me ‘Bai’ which means ‘friend’ in Bisayan dialect. His comment is in a form of question and not directly related to my blog post. He asked about the pros and cons regarding the use of ram pump to assist water distribution in my town. Here he goes:

Bai,
What would be the pros and cons of using a ram pump or a glockeman pump to assist water distribution of the manaay spring to poblacion Pio V. Corpus?


And here is my answer:

If you think installing ram pumps at the Manaay reservoir to assist water distribution to poblacion would solve the water supply shortage of the town – then, from an engineering point of view, you are wrong. But before I will tell you the how’s and why’s, here’s a little backgrounder of the Manaay reservoir.

The Manaay reservoir is surrounded by several small springs. The pictures above show one of those. The water flowing from these springs are pure; free of pollution. These springs are the main sources of drinking water. The downstream side serves as a laundry area.

The Manaay reservoir is a small concrete catchment tank built at the downstream side of Sitio Manaay spring. It collects and stores water from the spring and conveys it to the town’s water distribution system via a single 6” pipeline spanning between Manaay and Poblacion more than two kilometers in length. The spring is an abundant source of drinking water that it could supply at least three towns the size of Poblacion Pio V. Corpus. The volume of water delivered by the spring is so huge that only a fraction of the spring’s output is necessary to fill the catchment tank. The spring is situated at the forested area at the hills of Sitio Manaay about 2 kilometers south of poblacion. By virtue of its elevation, about 50 meters[for verification] above sea level, the reservoir has a built-in source of potential energy more than enough for distribution. No further pumping is necessary, as gravity alone would be sufficient to do the job.

As far as I know, the reservoir and the water distribution system of Pio V. Corpus were built in the late 60s, about a generation ago. Between the 60s and the 80s, there was no issue of water distribution problem in the town. The issue started to crop up only in the early 90s and lingers onwards. Households located farthest from the source were the most affected ones: there is no water supply at all. In some households, water is only available at night when most of the households in proximity to the source are no longer using water or have closed already their faucets. As the issue of water supply lingers, the technical word ‘WATER PRESSURE’ became a household phrase. The town’s people began to blame ‘decreased water pressure’ as the root cause of the issue.

While town's people continue to blame water pressure as the culprit of the problem, little did they know that the water pressure is not the real problem at all; it is just a technical outcome of the problem. The real issue lies on Municipal Engineering or the office that manages the municipal water system. They are not doing their job, or they don’t know what to do. They just watch as the issue arises, doing nothing. They failed to tackle the following issues and scenarios:
  1. That the capacity of the reservoir or catchment was, most likely, designed to supply the population in the 70s only. A further upgrade in the water system is necessary to meet the increasing demand as the population expands. The upgrade would mean replacing the existing pipeline with a bigger capacity or installing additional pipeline parallel to the existing ones to cope up with the increasing demand.

    Please try to check with the municipal engineering if there had been improvements being made to the water system during the period starting from the 80s onwards. These are during the terms of Mayor Avila and Mayor Amaroto. There had been reports that somewhere during their terms, there was an appropriation for the rehabilitation of the town’s water supply system.

  2. That the town’s number of households is growing and so does the population. Although I don’t have exact data showing the town’s population growth but by just looking at the Google map, the area of habitation has expanded in three directions: to the north, to the west and to the south sides of the center of the town. Where do you expect these additional households get their water? They all converged to the same water pipeline built in the late 60s.

  3. That the water system is getting older and becoming obsolete. Corrosion and siltation of water pipeline are inevitable. Over the years, the pipeline becomes corroded and silted, clogged up with dirt, thereby reducing the output.
As an engineer myself who grew up in town Pio V. Corpus, the only solution that I can suggest (aside from eradicating corruption in the local government) is for the municipality to build a new reservoir side by side with the existing one and a new pipeline. The new reservoir and pipeline must be built based on a feasibility study. There is no need for the old pipeline to be condemned: let it operate until it dies out. A story circulating among concerned Pio V. Corpus citizens on the Facebook has it that the municipality is planning to enter into a 50-million-peso loan with the Landbank; the purpose of which is unknown. I think building a reservoir or rehabilitating the town’s water system would be a very good justification.


Now back to the reason why a ram pump won’t work to assist the distribution of water from Manaay reservoir using the existing pipeline.

First, a ram pump, by its nature, is not designed to deliver a large amount of water. Also called an impulse pump, it is a device that uses falling water to lift a lesser amount of water to a higher elevation than the source. So, being primarily used for lifting relatively small amount of water to a higher elevation, the ram pump is not necessary in Manaay reservoir: the water source is already on the higher elevation relative to the point to be supplied. It would not be a good idea, of course, bringing the water up and then bringing it down just for the notion that it would increase the potential energy needed to deliver the water. The potential energy of the water in the reservoir is constant. It cannot be magnified by using ram pumps, as ram pumps derive energy from the potential energy coming from the reservoir. In a simple analogy, you cannot recharge a battery using its own power; some outside source must come in.

When water source is an issue, a ram pump is not a good medium for distribution; it is not efficient in terms of delivery. For a ram pump to operate, it needs at least seven times more amount of water than the amount it can pump. Meaning, if you want to deliver 1 cubic meter of water to an elevated location, you require at least 8 cubic meters of water to operate the pump - 7 cubic meters of which will be used to drive the pump and goes directly as waste.

To understand fully how a ram pump works, here’s an exerpts from Wikipedia:

  • Construction and principle of operation

    A hydraulic ram has only two moving parts, a spring or weight loaded "waste" valve sometimes known as the "clack" valve and a "delivery" check valve, making it cheap to build, easy to maintain, and very reliable. In addition, there is a drive pipe supplying water from an elevated source, and a delivery pipe, taking a portion of the water that comes through the drive pipe to an elevation higher than the source.

  • Sequence of operation

    Figure 2: Basic components of a hydraulic ram:
    1. Inlet — drive pipe
    2. Free flow at waste valve
    3. Outlet — delivery pipe
    4. Waste valve
    5. Delivery check valve
    6. Pressure vessel
    A simplified hydraulic ram is shown in Figure 2. Initially, the waste valve [4] is open, and the delivery valve [5] is closed. The water in the drive pipe [1] starts to flow under the force of gravity and picks up speed and kinetic energy until it forces the waste valve closed. The momentum of the water flow in the supply pipe against the now-closed waste valve causes a water hammer that raises the pressure in the pump, opens the delivery valve [5], and forces some water to flow into the delivery pipe [3]. Because this water is being forced uphill through the delivery pipe farther than it is falling downhill from the source, the flow slows; when the flow reverses, the delivery check valve closes. If all water flow has stopped, the loaded waste valve reopens against the now static head, which allows the process to begin again.

    A pressure vessel [6] containing air cushions the hydraulic pressure shock when the waste valve closes, and it also improves the pumping efficiency by allowing a more constant flow through the delivery pipe. Although, in theory, the pump could work without it, the efficiency would drop drastically and the pump would be subject to extraordinary stresses that could shorten its life considerably. One problem is that the pressurized air will gradually dissolve into the water until none remains. One solution to this problem is to have the air separated from the water by an elastic diaphragm (similar to an expansion tank); however, this solution can be problematic in developing countries where replacements are difficult to procure. Another solution is to have a mechanism such as a snifting valve that automatically inserts a small bubble of air with each pump cycle. Another solution is to insert an inner tube of a car or bicycle tire into the pressure vessel with some air in it and the valve closed. This tube is in effect the same as the diaphragm, but it is implemented with more widely available materials. The air in the tube cushions the shock of the water the same as the air in other configurations does.

    The optimum length of the drive pipe is five-to-twelve times the vertical distance between the source and the pump, or 500-to-1000 times the diameter of the delivery pipe, whichever is less. This length of drive pipe typically results in a period between pulses of one-to-two seconds. A typical efficiency is 60%, but up to 80% is possible. The drive pipe is ordinarily straight but can be curved or even wound in a spiral. The main requirement is that it be inelastic, strong, and rigid; otherwise, it would greatly diminish the efficiency.

    Some later ram designs in the UK called compound rams were designed to pump treated water using an untreated drive water source, which overcomes some of the problems of having drinking water sourced from an open stream.
    A Ram Pump in action

  • Common operational problems

    Some common operational problems are intrusion of air into the drive pipe, blockage of the intake or valves with debris, knocking due to having too little air in the pressure vessel, freezing in winter and bursting of the delivery pipe if output is blocked or pressure not relieved.

13 comments:

  1. engr,
    thanks for the insight. despite the shortcomings of the ram pump, i am still convinced of its potential to supply water albeit in a more limited fashion to pio v corpus given the dire power supply situation and finances of the said town. i would like to see it succeed in supplying for example drip irrigation for vegetables, drinking water (coupled with bio sand filters) to nearby areas in a smaller, more efficient and sustainable manner. my inspiration for this would be the ram pumps of auke idzenga (http://www.ashdenawards.org/files/reports/AIDFI_2007_technical_report.pdf) who won this award most recently (http://www.theworldchallenge.co.uk/producer-project08.php). hope to hear your thoughts on this.

    ReplyDelete
  2. Hi,
    I read both the references you mentioned above about some applications of ram pumps. I don’t have any qualm about it. The benefit of using ram pumps is, indeed, undeniable. Take note, however, that both the references/documents talked about ram pump as a device to lift water to an elevated location. Never in my reading that the documents mentioned ram pump as being used to bring water down from a source.

    To make my point, there are two scenarios when delivering water from a source - as I learned from ‘hydraulics subject’ during my college days. These are as follows:

    1.) Bringing the water down:
    When the water source is at a higher elevation, gravity will do the job for you to bring the water down. In hydraulics, the energy stored in the water due to gravity by virtue of its elevation is known as potential energy. This energy is what makes the water move down along a pipe. As the water moves along the pipe, potential energy is converted or translated into kinetic energy. Kinetic energy or energy of water in motion is the very same energy that runs the ram pump.

    2.) Lifting or Bringing the water up:
    You lift the water when your target location is at a higher elevation than your source. This calls for the use of pumps. And any kind of pump will work, whether it’s an electric pump or a ram pump: they both serve the same purpose. A ram pump will come into play when we don’t want to pay electric bills.

    While a ram pump may be of great use for purposes you mentioned, it won’t work to increase the water output from the Manaay reservoir. Further, you will certainly not use a ram pump to bring water down from the reservoir.

    Just one question: are you a kababayan?

    ReplyDelete
  3. engr,
    i have some relatives there. and i wondered why they had to buy bottled water. and during one visit to manaay, i didnt think that the reservoir was in operation. i thought that it was condemmend, another white elephant used to fatted somebody's pocket. moreover, i would prefer ram pumps to deliver water to less privileged areas in pvc since i dont think electric water pumps will cut it given the power situation in masbate wherein 2 hr brownouts are a daily occurrence.
    tks

    ReplyDelete
  4. While a ram pump may be of great use for purposes you mentioned, it won’t work to increase the water output from

    THANKS FOR THE ABOVE CLARIFICATION

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  5. Redeem I surely admire your knowledge about rum pump I hope I could adopt this method and help my kababayan for their drinkable water supply. I had the time to handle KALAHI-CIDSS projects for water supply but it was implemented by some inexperienced engineers of kalahi-cidss and layman persons an ordinary foreman and mason/plumber with the toleration of the mayor

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  6. I mean a ram pump method of supplying drinkable water (sorry I misspelled)

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  7. Amie, I read your post about KALAHI-CIDSS projects. I also visited DSWD website and learned more about these projects. Reading your blogpost, i understand your predicament. It's all about the immortal issue of corruption... Well, what else do you expect from politicians?

    ReplyDelete
  8. Dupont Hydro is a leading manufacturer and supplier of hydraulic cylinders tubes, hydraulic cylinder rods, jacks, power packs and repairs.

    ReplyDelete
  9. Redeem, please consider that the design itself of the water system of PVC (from source to distribution) was changed from the original concept of the 70's. You are right in saying that the design load of the original system was reached already and that a new design should be made. Sometime in the early 2000's, a study was conducted by Dr. Apostol, a hydraulic engineer. In that study, they surveyed the area and concluded that the head at the source was higher than that of the town itself so the logical move would be to maintain that head and construct a reservoir at the source. The most illogical move made was that somebody constructed the reservoir much higher that the source. Water should be pumped up to the reservoir if that reservoir should be used, though by inspection, it would not pass as a structurally sound tank. This is where ram pump is needed, not to deliver water to the town but to lift water from the source to a much higher reservoir. That reservoir was situated in a much higher head (a bigger potential energy which is good). Ram pump delivery volume should be greater than the required volume of the town. Else, the reservoir will be dry. Roughly, about 4 to 6 six ram pumps of about 200mm dia are needed for the purpose. Ram pump supply head for PVC case is as small as 1.5 meters. This should be verified by computations.

    Problem number two, the distribution lines running around the town was based on the assumption that the user will tap on the pipe running infront of their house. Based on that, pipe sizes and volume computation were made to provide a uniform water pressure for every household. That is still correct and logical. BUT... the pipeline around town was laid before the reservoir problem was solved resulting in a limited water supply and pressure from the source. Everybody was complaining why some households has water and the others have not. Some has high pressure and some just drips of water. What they did? They tapped their water lines from areas with high water pressure. Some even bought rolls and rolls of HDPE pipes so that they can tap their pipe from source two blocks away. From design point of view, this move changed everything. It changed the assumptions made during the design.

    We are both products of that town. I suggest we both come up with an alternative design and offer our services free of charge so that everybody would benefit including your family and mine. The only problem now is implementation, well, that is another story.

    Also, we should educate everybody on the proper use of water and how to conserve water. Time will come that water will be scarce. They should pay a decent amount for the maintenance and care of the water system. Facebook is a good venue. I've read some comments from Marne Cabatingan and from others of donations for the rehabilitation of the system. That can be a good start.

    Please keep in touch.

    ReplyDelete
  10. Dong,

    Thanks for your time time. I will write comments soon. So busy with office work pa... Too many deadlines.

    ReplyDelete
  11. Redeemer..your discussion offers profound insights to the REAL problem regarding the water system of PVC... i just hope that the LGU will come across this blogspot.

    ReplyDelete
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