Civil Engineering Question - water supply

Factual Questions
1

Our neighborhood is in the middle of a zoning battle. We live in a small neighborhood that was built out in the sticks 30 years ago, but the city has been growing and we’re about to be engulfed.

We’re built up the side of a hill - my house sits at about the highest point for at least 30-40 miles in all directions. (We’re not talking mountains here, this is Oklahoma plains.)

A developer has purchased the surrounding land and is trying to rezone to a higher population-density level. (The area was zoned with restricted density originally, because of limitations of the sewer system.) According to the developer and city engineer, the sewer situation is no longer a problem (I’ve not yet gotten a good explanation why).

We already have water-pressure problems. Filling a glass of water from the refrigerator-door takes forever. There’s a noticeable drop in shower flow when you turn on the kitchen faucet across the house, much less turn on a garden hose or water-using appliance. My shower occasionally quits completely for several minutes with no other water running (no one else home), which I can only guess is due to something a neighbor is doing. It’s not a problem with my house - our neighbors can tell similar stories.

We’ve presented our complaints at two planning commission meetings so far, and will go before the city council in the near future. We’ve mentioned the water problem at both meetings as reason to NOT rezone.

Last night, the city engineer claimed that the new development would actually fix the problem. He claimed that adding a row of houses behind us (all there’s room for) would “close the loop” and improve the water pressure for our neighborhood. Considering that the man is generally known to be in the developers’ pockets, I’m rather suspicious. Without going into details, he’s already demonstrated that he’s willing to overlook and/or excuse egregious (if not downright illegal) failures on the part of the builder in this situation.

So, are there any civil engineers here that can explain what he’s talking about and give me some idea if this is legit, or if he’s just making it up?

If more info is needed, just let me know what.

Thanks for any info!!

2

This not my area of expertise, but I know a little about groundwater and I have NO idea what he means about “close the loop”. I share you doubt about his objectivity in this matter.

Concerning your water pressure/flow rate problem, I would call a local well driller (there should be a lot in your area) and see about having you well deepened or a new well drilled. If your water pressure/flow rate problem has slowly got worst over time, you may need to get your well developed (cleaned). Rust, sediment, etc. could effect the flow over time. Like I said, call a local well driller for his advice and expertise.

LL

3

Also I forgot to mention that your well pump may be slowly dying. Again, check with a well driller.

LL

4

I’m going to going to assume you’re on a municipal water supply rather than a private well - otherwise, your pressure problems shouldn’t be affected (too much) by the adjacent development. Short answer, I have no idea what the city engineer means by “closing the loop.” In a municipal system, the distribution system (I guess that’s the “loop”) is already closed - that’s the only way to maintain adequate pressure in it. Adding more connections (for additional houses) can’t do anything but reduce the overall pressure.

The only way I can see that would improve the situation is if the new development forced the city to add capacity (either quantity or pressure) to the drinking water system. Adding flow means either ramping up production in the existing wells or drilling new ones (unless you’re pulling from surface water), and it may also require additional treatment processes; adding pressure means building a taller water tower. Either way, the engineer would probably be talking about real improvements instead of closing imaginary loops. Based on the information in your OP, it doesn’t sound like any of those improvements are planned.

Can you measure the water pressure at your house? Oklahoma requires a minimum of 25 psi at any connection to a public water supply, even during peak flows. If you’re close to or under that now, you might be able to bring that up at the city council meeting.

5

Here is what “closing the loop” means: Imagine your nearby water mains are U shaped. (With the feed connecting to the bottom. Maybe I should have started with a Y?) If you’re near one of the ends of the U, the water pressure is lower. If more pipe is put in to convert the U to an O, you’re no longer on the end. But the pressure only goes up if the pressure at the other end of the U is higher than yours. Otherwise it can actually make things worse. That is assuming that they actually close the U. They no doubt “promise” they will but they won’t.

I pity you’re situation. I also live in a developer controlled county.

6

You have the physical situation pretty well understood. The way it is often stated is that you are on either a radial feed or a loop feed. A radial feed means that your water line comes as a single line out from the mass of water piping in the central city, as a single line from the center of a circle along a radius (it is a figure of speech and notlikely to be a direct radius.). Your pressure then depends on the size of that line, the flow through that line, the distance the water must flow, and the height of your neighborhood compared to the water tower.

Closing the loop means running a separate radial feed out to your area, and connecting the two lines. If yours is an old developement, it is entirely likely that the new water line on the second imaginary radius is much much larger. The larger line will have less pressure drop as the water flows through it. It might be large enough to improve your water pressure. If it is no larger than your line, then it still might improve your pressure if there is very little use on the other line. Other than that, all it does is improve the city’s ease of maintenance by allowing them to shut off one line and still feed you water from the other.

7

I beg to differ, though. It’s not an open-ended “U”, per se because the far end must be terminated at the last user. Otherwise, they’d be losing product which woul either have to flow where? Back to the treatment plant…or into the wilderness…both of which wastes their product, time and materials, energy, etc. Therefore, it must be, what is called a closed system.

I’d ask him to define that “close the loop” term better BECAUSE the loop IS ALWAYS closed BECAUSE they don’t waste water! An open loop system can, in theory, exist, but water companies would be wasting a lot of energy, materials, wear-and tear on the treatment plant, pumps, etc…if he’s trying to say potable (drinking) water is presently flowing back “freely” to the water treatment plant! Via what? Directly into the sewers??? C’mon! (For emphasis, understand I am talking about potable water does not flow unused based to the treatment plant…it’s highly inefficient.)

Assuming you must be talking about a municipal water system, water is typically pumped from the water treatment plant along a (feeder?) main into water towers. Often, this is over a great distance, so a series of (booster) pumps provides the necessary extra push along the way. From the tower, water flows by gravity to a supply main. The supply main has smaller branches coming off it to your house. When you open a faucet, you’re really opening a valve. Water flows into your sink, for one.

It sounds to me that the existing system must be undersized. Adding more homes on the same system will only exaserbate the situation. You need another water tower added to the system, I’d wager, to get the correct pressure in the system for all users to be happy, or not being a Civil Eng (CE), I WAG that an extra pumping station is sometimes placed along the supply line to help improve water pressure to houses - perhaps as an economical solution to supplement the available pressure as demand grows.

Likewise, what about the sewers? Are you guys on a system or septic? This may add addition constraints…hopefully a CE will come along to elaborate on this aspect of the problem.

FYI: Mechanical Engineering overlaps into many areas. I know the hydraulics of this, but a CE would know the code and best practises. - Jinx,

8

This should have read as follows:
(For emphasis, understand I am talking about potable water…the good stuff that just came from the treatment plant. Potable water does not flow unused back to the water treatment plant…it’s highly inefficient.)

At least, I can’t imagine why ion the world they’d operate with some kind of open-loop, or open-flow system. - Jinx

9

Yes, this is a valid method, often used by chemical plants when production demands outgrow an existing (pipe) line size. However, I’ve never heard this described as “closing the loop”…which gives me a different picture concerning open loop (or open flow) systems vs. closed loop (or closed flow) systems.

Just wanted to clarify…

  • Jinx
10

Lest I upset any civil engineers here, you may not have a water tower. I always see water towers in “hick towns” (no offense). Here in big 'burbs, all water pressure is the result of pumps. So, for example, during our great blackout last August, we lost water pressure because we didn’t have the luxury of a water tower. But my family up north – also blacked out – has pressure the whole time because even though their community buys the same water, they were fed by a tower.

So, I’m not trying to be contradictory. I’m trying to say that you should investigate your municipal water system in its totality and see exactly what capacity they have to support additional development. Of course you’d be fighting a city organization intent on gaining an additional tax-base, so who knows what luck you’ll have.

11

Jinx. Think about it for a second. Do you really believe that I or anyone else posting here actually believes that water companies have uncapped pipe ends?

Of course the ends of the U are capped! How could anyone think otherwise?

In the meantime, I realized something that actually might be good for the OP. One common reason for decreasing pressure over the years, esp. if the water is hard, is that the mains get increasing clogged with mineral deposits*. If a new line is connected to the end of your old line (and you are kinda close to that point) you might get better flow.

  • Which would mean you could have great pressure during low demand, but still poor flow.
12

No, ftg, no you per se, but (a) following the progression of the thread keeps things in proper context. The meaning to this term “closing the loop” was questioned by several at the start of this thread. Hence, in light of that frame of mind, the example of the “U” picture can be misunderstood…as if it were open-ended.

…And, (b) there are open-flow fluid-delivery systems and yes, they can still be pressurized (above what is deemed atmospheric) in a slightly different manner than a closed system…for different purposes. As I said, the term (phrase) in question has a different meaning to me because of this…and (c) I had not heard it used in this context, as I had confessed…could lead one to believe they are leaning towards trying to tell the residents anything…and (d) experience teaches you got to watch those developers carefully.

Sorry to have ruffled your feathers, ftg.

  • Jinx
13

Maybe a Civil can explain alternate options to this: Water towers also act as accumulators to deliver consistent flow downstream by reducing “hydraulic response” from, well, pumping for one, skipping the details. Yes, even “Big Burbs” and large cities have water towers…often of a more modern design than the stereotypical “hick town” look. Some contain more than one tank on the inside to be multifunctional while conserving the space otherwise needed for a pair or group of water towers.

So without them, what do you do? I guess there could be stations along the line to dampen out such effects…or other design variations?

14

A water tower is an old, but effective, technology. Water towers were used everywhere in the US until the last 15 or 30 years. The main purpose to a water tower is to maintain a consistent system pressure. The pressure at the base of the water tower is equal to the height of the water in the tower. As the water goes out of the tower, the treatment plant or well pumps water back into the tower. the water height in the tower only varies by a relatively small amount. This height change is less than the pressure surges that you would otherwise get from fixed speed pumps starting and stopping as load changes.

The pressure at your house when no water is flowing in the system depends on the elevation of your house in reference to the water tower. The tower is usually as high as possible in the town, so if you are are the lowest point in town, your house might have extra high pressure. A single water tower can provide pressure for an unlimited area when there is no flow. This is the static pressure.

But of course there is never no flow, and there is certainly never no flow at the times that you want to use water. How much the pressure at your house drops from the static pressure depends on the size (and condition) of the pipes between the water tower and your house, and how much flow is going through those pipes. The smaller the pipe and the longer the distance, the more the pressure drops. Old piping and areas with poor water treatment can get encrusted with tubercules on the inside. It is not really the same as hard water deposits. The tubercules are nodules of rust and organisms that live in the rust. Modern piping with modern water treatment rarely crusts up, but old pipes that crust up do cause quite a pressure drop.

So, you have low pressure. Assuming that you are not higher than the water tower, your low pressure is caused by the single pipe feeding your area being too small for the distance it has to flow, and the amount of flow it needs. The options to improve this are to either decrease the distance between you and the water tower, or increase the pipe size between you and the water tower. Adding pipe is often cheaper than a new water tower, since the new water tower would require pipe back to the treatment plant also.

If there is already a larger, lightly used, pipe in the area, connecting between your pipe and the other larger pipe acts like adding a larger pipe between you and the water tower.

Modern technology allows methods that do not use water towers. The goal of a water tower is to provide constant pressure. Variable speed drive pumps can be used at the treatment plant to maintain a constant pressure out even when the flow changes greatly, as long as there is always at least some flow. When the use drops off, the pump slows down, when the use picks up, the pump speeds up. For some cities, this is more cost effective than a water tower.

I have heard (not seen or know for sure) that British water systems used to have water tanks in every house to act as their own local water towers, but that this is being eliminated in more modern areas.

15

As I said earlier, we’re on a pump based system. The blackout last August killed our water supply instantly – not after a certain amount of time because a tower drained, but instantly because the pumping stations all died, too. Okay, there was a little bit of pressure in the system, so we had some flow for a couple of hours.

Oh, but I’m not trying to reiterate what I said above. I have a new point:

I live in the Great Lakes. We have so much fresh water that we laugh (or feel sorry) at the poor people that live, well, virtually anywhere else. Water shortages? Conservation? Brown lawns? Expensive rates? We have all the water anyone in the world could want, and it’s good quality, and it’s exceptionally cheap. But…

…yeah, we have “voluntary” water conservation at certain periods in the summer (actually, neighboring cities have mandatory conservation, so I’m lucky). Things like odd-numbered houses can only water on odd-numbered days, and vice-versa for even numbers. And I blame it on the lack of water towers. The explanation always given is that the consumption will increase pressure in the distribution systems resulting in water main breakages – I’m guessing that the pumps would tend to over-compensate because of the constant drain that should result in a low-pressure condition. And the clincher: on these conservation days when we shouldn’t water the grass, every once in a while the DPW or fire department will be out opening fire hydrants because for some reason, the pressure got to be too high and this is the best way to lower it!

So, I’m thinking that either better pumping logic or the reintroduction of water towers could stop all this silliness. I live in Michigan for God’s sake – water is my birthright!

16

Hmmm. This is my best guess at an answer. Based on logic, not fact.

In order to maintain a constant pressure using variable speed pumps, the pressure must be measured somewhere. I would assume that it is somewhere a moderate distance from the treatment plant, in order to measure a more steady pressure (this is standard practice).

If demand (flow) goes up, the pressure pressure drop through the system begins to rise, and the pressure at the measurement point will start to fall. The pumps then ramp up and push more water into the system. This will raise the pressure is all the pipes UPSTREAM of the measurement point to counter the increased pressure drop through the increaed flow, to maintain setpoint at the measurement point. This upstream portion could be a large section of the jumble of city piping. So the Fire Dept may be opening hydrants in various areas upstream of the measurement point in order to drop the local pressure there.

Would water towers solve this problem? Yes, in a way. Water towers have a maximum pressure based on height. But if the demand got too high for hte size of pipes (as it sounds like you have), instead of the pipes breaking, you would just get your water pressure down to a trickle in high demand times. Real answer is more and bigger pipes in the ground. Which adds up to increased water bill. Maybe that’s why your water is so cheap, they have not maintained the system to match population growth.

17

I would have thought people in Michigan would have never wanted for water.

Well, I’ve lived in dry West TX for many years. (water was pumped from a lake about 120 miles away) We never had to conserve water. There was a local storage reservoir and of course we had some of those “hick town” water towers. You know the kind that can supply water for days without electrical power. Also our water supply was a constant 80 PSI. :cool:

I now live in AR, we live on a lake (we have city drinking water but use the lake for yard sprinkler system)… no “hick town” water towers but one must have a pressure control regulator upstream of the house to maintain a safe pressure. I have mine set at 60 PSI.

18

Thanks for all the info! Can someone tell me how to measure the water pressure at my house? Since it definitely sounds like I’ve got valid suspicions, I think I’ll call the university & see if they have any CE profs that would be interested in giving us a hand.

Yes, I’m on the city water system. We do have some water towers, but they’re not building any new ones, so I think they must’ve switched to a pump system.

We don’t ever have good water pressure, so I’m guessing it’s not just mineral deposits. This addition was several miles outside of town proper when it was built, & as I understand it they never finished developing because they couldn’t provide proper services for any more houses.

Supposedly the sewer & water is all going to be just fine, though. :dubious:

The saddest part is, it’s not the developer saying this stuff - I know he’s a liar, he’s proved it. (Not least, he told residents a couple of years ago that he wouldn’t be asking for any zoning changes, which is why we’ve been taken by surprise on this.) It’s the city planning department that’s lying to cover his ass.

I don’t have the maps in front of me, but I know that they were tapping into existing water lines, rather than bringing in new pipes. That’s what made me suspicious of his statements to start with. I know that physics can sometimes be counter-intuitive, but I don’t see any way that adding more outlets to an existing system is going to improve pressure.

If I can get proof that current pressure’s too low, I’ll take it in. So far they’ve managed to ignore or gloss over every other legal problem we’ve brought up, but they are getting spooky. If we can stack up a few more, we may make it.

I really really really wanted to stand up in the planning commission meeting and ask this guy for his personal, written guarantee, one that would make him and the city liable if he was “in error” and the sewer & water services can’t meet the development demands. I mean, after all, if he’s that sure it’ll all be OK, that shouldn’t really be a problem, right? I’m going to find some way to do it at the city council meeting. They’re elected & therefore more susceptible to public opinion.

Thanks again for all of the help! Y’all are the best!!

19

Didn’t mean to offend, olefin – the town I grew up in had a huge, modern water tower, so I guess you could call me a “hick,” too.

Here in the Detroit area, virtually all of the water comes from the city of Detroit water purification system. It’s a big political issue for everyone. But, the infrastructure hasn’t kept up with demand. We have plenty of water, just not all of the required distribution to meet true peak demand. So, I imagine there are many, many pumping stations all over the place. AFAIK, no one pays the city of Detroit for water; the individual cities pay Detroit, and charge us. Apparently even people in Detroit don’t pay for their water (okay, okay, that’s part of the political issue).

So, your logic sounds like a good explanation.

20

First, you can get a water pressure gauge at a hardware store that will screw on to a hose bibb. Once you have one, you can measure two things: the pressure at your house with no water running (that is, screw on the gauge, make sure that no other water is running in the house, and then open the hose bib to measure the pressure). Then, go an open a faucet somewhere else in the house, run back to the gauge and see what the pressure is with the faucet open. While you are at it, measure the flow rate at the faucet using a gallon container and a stopwatch. That will give you a good idea of your water supply. My water supply gives me about 5 gallons per minute (I think) through a 3/4" supply pipe from the street main to the house.

You can also open up two valves and measure the pressure and flowrate again. Since you have problems with more than one faucet running, I expect you’ll have a difference in the readings. Heck, now that you have the $5 gauge, lend it to a neighbor and let him use it to get an idea of how you compare.

Now, a more important point, and perhaps a way to get the town officials to act responsibly. As noted by others, the fire hydrants are usually on the same water line as the domestic water (though not always, some communities have dedicated fire mains). If you ask, the fire department should come out and do a flow test on a nearby hydrant (it’s not a big deal, and they probably are required to do it anyway), and they should also be able to tell you what the minimum requirements are. So specifically ask at the planning commission meeting if the water mains will provide enough water for fire fighting (and take the time before hand to find out what those requirements are). It will be taken seriously because insurance companies won’t like it if there isn’t enough water for fighting fires, and developers will find it harder to sell properties if insurance is expensive or impossible to get.