Energy from gravity fed water lines, bullshit or useful? - Page 1
Forum section: electronics / general

author: ja450n
author_rank: Newbie
timestamp: February 23, 2015, 05:11:11 pm
content: I recently came across a news article about a company called Lucid Energy that is installing turbines in gravity fed water lines to generate electricity.Is this BS like solar roadways, or is it actually potentially useful?News Article:https://www.minds.com/blog/view/415942000412463104/portland-installs-turbines-in-their-city-water-pipes-powers-city-by-flushing-toiletsThey also have a 'Technical FAQ' on their site that claims the turbines use 1-5 PSIhttp://www.lucidenergy.com/wp-content/uploads/2013/08/FAQ_Riverside_July2013.pdf

author: mtdoc
author_rank: Super Contributor
timestamp: February 23, 2015, 05:48:27 pm
content: The energy potential from hydro isfairly straightforward to calculate. It basically comes down to the product of head x flow.That link looks like they are using their turbines in water mains - VERY large pipe diameters - which will meanpotentiallyhigh flow rates. As long as there is some reasonable amount of head then in theory a good amount of electricity could be produced.As far as what the practical limitations and potential complications of putting a turbine in a water main are - I have no idea.

author: SeanB
author_rank: Super Contributor
timestamp: February 23, 2015, 06:18:27 pm
content: It works if you do not have water metering, or if you are lucky enough to have a property with both a stream that is perennial and which is on a very steep slope so you have a good static head. There was a nice set of articles ( location escapes me ATM but it was in South America) of an off grid house, powered using a local stream that was diverted to drive a pelton wheel and drive a generator to provide power, with the power line loss being reduced by using 2 transformers to up the voltage to 2kV for transmission, and then using standard copper wire in a conduit. He essentially got free power and water, along with heating for his locally built well insulated round house.

author: IanB
author_rank: Super Contributor
timestamp: February 23, 2015, 06:39:46 pm
content: This whole area needs proper calculation of energy and power before it can make sense. For instance, if you are pumping water along a pipe it takes power to do that, so putting a turbine in the pipe will simply suck out the power that you already paid to put in.Secondly, if water is flowing downhill due to gravity, then perhaps you can extract power out of that by means of a turbine, but if you do that you will lose pressure for later delivery of the water to consumers. How did the water get uphill in the first place? Did you use power to pump it up there? So you may still not get a benefit, unless you have excess pressure that you don't really need.In short, any time you try to take power out of a system that power had to get put into the system somewhere upstream. Power recovery systems only make sense if the power you are recovering would otherwise be going to waste. It needs accurate analysis to get this right.

author: mtdoc
author_rank: Super Contributor
timestamp: February 23, 2015, 06:40:54 pm
content: SeanB - you are talking about microhydro - which can work well for select properties with the water resource as you describe. I'm going to be installing one (Powerspout) on my property soon (I have a stream running through my property).The OP's link was to a company installing turbines in the very large diameter water mains pipes in large cities (Portland, OR in this case).

author: LabSpokane
author_rank: Super Contributor
timestamp: February 23, 2015, 06:54:22 pm
content: Portland's water flows down hill from a reservoir located essentially on the slopes of Mount Hood, a volcano just to the east. They are likely losing little to no pressure or flow from a micro turbine and can likely use the energy to offset the boost pumps necessary for city distribution.Www.portlandoregon.gov/water/48904Not pseudo science.

author: IanB
author_rank: Super Contributor
timestamp: February 23, 2015, 07:07:35 pm
content: Quote from: LabSpokane on February 23, 2015, 06:54:22 pmThiscouldexactly be pseudo science. Pumps produce "head", which is the equivalent elevation of the water to produce the same pressure. If the water in the reservoir is 1000 ft up the mountain it has 1000 ft of head. This head is what can allow the water to be distributed around the city without the need for any boost pumps. If you keep the pressure and don't lose it you have free energy.Now then, if you put turbines in the downhill pipes you take away some of that potential energy and convert it into electric power. That's good if you have surplus head and you don't need all of it. But if you do need all of it then you will be robbing Peter to pay Paul, especially if you put some of that generated energy back in the system later on through boost pumps. All you have then done is introduce inefficiencies into the system and wasted some energy.

author: LabSpokane
author_rank: Super Contributor
timestamp: February 23, 2015, 07:29:47 pm
content: Quote from: IanB on February 23, 2015, 07:07:35 pmIf this is your argument, you should contact BPA and let them know that all of the hydroelectric dams that are along the Columbia River don't work. Not one of them, not even Grand Coulée has 1000 feet of head.And for reference, Mt Hood is 11,250' tall and Porland is 50' above sea level. The watershed from whence the water originates is around 4000' MSL. The average water tower in the US is about 150 to 200' high which gives about 65 to 85 psi of pressure.Nobody's toilet is going to go burp because of a microturbine in the water line here. There are lots of bullshit energy projects to rail on. This isn't one of them.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 23, 2015, 08:11:59 pm
content: I really suspect Portland knows what they are doing, but it might be necessary to dig another layer or two to get all of the story.For example, with the several thousand feet of head potentially available you in theory would not need any pumps to do water distribution. That is plenty of power to push it anywhere in the city. But a closer look would show problems. Friction losses cause steady drops in pressure, and there are limits to the amount of pressure you can have at any delivery point (unless you want to pay for a lot of pressure regulators at the local taps). A turbine in a downhill section of the pipe could capture the energy and send it over wires (which have lower flow losses) to pumping stations in relatively flat sections of the city.The same thing could be done purely mechanically using high pressure hydraulic lines for power distribution, but the electrical infrastructure is already there, and is generally more reliable than hydraulic systems.

author: IanB
author_rank: Super Contributor
timestamp: February 23, 2015, 08:21:31 pm
content: Quote from: CatalinaWOW on February 23, 2015, 08:11:59 pmThis is all true. The difference between success and failure, economic vs. uneconomic is all about accurate analysis, which is what I said above. If you get your analysis wrong you can waste money. It is to be hoped that the water authority there does have a correct and accurate economic and engineering analysis.

author: LabSpokane
author_rank: Super Contributor
timestamp: February 23, 2015, 10:24:47 pm
content: The problem with the energy business is that there are so many hucksters that it's easy to assume all projects are shit until proven otherwise. This particular project is not in any way violating the conservation of energy, good engineering practices, or replicating some type of known failed system. These types of systems are well understood and offer excellent efficiency.Portland uses 35B gallons per year which translates to about 12.5 MWe of theoretical electrical power assuming a 1000' drop. Even if the end result is capturing 20% of that, it's a good energy project since the capture mechanism is paid for and there are no fuel costs.And as explained in the link I posted, Portland has some elevated regions that require pumping - even though the reservoir is well above the city.I'm all for calling out bad energy developers. That said, let's do everyone the courtesy of some basic arithmetic before we burn them as witches.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 23, 2015, 11:53:47 pm
content: The purpose of pressurizing the water main is so that, after distribution losses (drag and leakage), there is still enough pressure at the house to deliver water up several floors at enough pressure to enable spray type fixtures like sprinklers, sink sprayers, shower heads and so on. There will be a standard somewhere stating what the minimum should be.So the question might be, are they supplying too much pressure? Quite likely! Can that be used as a source of power? The excess above customer minimums, yes. Who knows how much that is? Excellent question!So, as with any other quack claim, the conclusion is simple: it might be possible, no it's not worthwhile, and please don't give it unnecessary attention.Tim

author: LabSpokane
author_rank: Super Contributor
timestamp: February 24, 2015, 12:14:28 am
content: You're misunderstanding what they're doing. The lines currently will require pressure regulators in whatever form in order to not over pressurize the system. If the system was a straight downhill run for 1000' vertical drop, the pressure at the bottom would be over 400 psi. Why not bleed some of that energy off with a few turbines? The current water delivery system wastes energy. This is NOT a case of putting a wind turbine on top of your car.There's things to be concerned about the company in question. They are small and their device is new. However, it should be noted that their device has passed muster with the bank's engineer as well as licensed PE's at PG&E, who knows its stuff when it comes to hydro. I read Lucid's site and nothing is jumping out at me as BS. They are advertising capacity factors in the neighborhood of 60%, which is right in line with what I would expect with such small generators.In turn, Lucid was awarded a 20 year power purchase agreement. This means that the utility sees a very manageable financial risk and that additionally, Lucid and their investors and bankers are shouldering most of that risk. A PPA is a liability on the balance sheet. So there is a bit of risk on the utility side.If you think the engineering is shit, show me your math. Thus far, my napkin shows that this is a plausible generation technology.I have to wonder why you folks believe that capturing energy from water running downhill is some type of pseudoscience or bad engineering.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 24, 2015, 01:02:05 am
content: Who the hell puts their water reservoir 1000 feet up?I mean it's not like houses are ever more than 50 feet up or down, relative to each other. Around here... Oh...Anywhere pressure has to be bled off, can always be done at an advantage, yes. Wait, you mean they don't already do this? Sounds too easy and obvious... I mean, there are plenty of dams and turbines on fresh water resources, which eventually become drinking water sooner or later. Maybe they can't once it's been collected and "blessed" as Federal Drinking Water?Suppose I should actually read the article instead of just responding to other posters' idiotic comments...Tim

author: IanB
author_rank: Super Contributor
timestamp: February 24, 2015, 01:50:02 am
content: Quote from: LabSpokane on February 24, 2015, 12:14:28 amNo one has said that it is. I don't know why you are posting so much stuff trying to counter a position that has not been presented in this thread?

author: IanB
author_rank: Super Contributor
timestamp: February 24, 2015, 01:58:06 am
content: But since numbers are important, here are some numbers from the LucidEnergy FAQ: (emphasis mine)Quote"100 kW""more than a MW"A whole MW. That's really not very much electricity at all. It's like the proverbial drop in a bucket.The short answer is what I wrote above. You can only recover energy if what you recover was otherwise going to waste.So if you let the pressure down from 200 psi to 100 psi through a valve, you are wasting the energy. If you let the pressure down through a turbine you can recover some energy. But this only works if youneedto reduce the pressure for some system reason. If you don't need to reduce the pressure and you reduce it anyway you have merely introduced losses into the system with a net cost associated.If you have only a tiny bit of excess pressure to dispose of, then you can only recover a tiny bit of energy. That's how energy balances work.

author: LabSpokane
author_rank: Super Contributor
timestamp: February 24, 2015, 03:48:45 am
content: Tiny amount of pressure? 400 psi over a 1000' drop is tiny? And pressure drop isn't the same as energy.1 MW is not an inconsiderable amount of energy and putting 10 of these gensets in line is really not a big deal, btw. Go look at a 1MW ICE genset and come back and tell me how "tiny" it is. Go try to power 1000 homes for 24 hours and tell me how easy it was for you. No, it's not a 1000 MWe nuke plant. Many thermal plants are in the single to low double digit MWe range. This is certainly on the scale of run of the river hydro plants (which is what this is). It is also certainly on the scale of small scale solar - and best of all - it's *baseload* power, which is more valuable.We Americans are so spoiled with our power prices, we completely forget how hard it is to generate a measly 1MWe of base load without hydro, fossil fuels, or nuclear. It's a lot of power. And welcome to the reality of the 21st century. The low hanging fruit is gone, and new power generation will be distributed, small-scale and more expensive. Why? It's all that's left to develop.And I'm spending a lot of effort, because you're challenging the legitimacy of a *bankable* power project, albeit a small one, with absolutely no capacity or willingness to evaluate its true merits. You have produced nothing to demonstrate that it's a bad project. Yes, they are small gensets. But they are not lying about that. They do not appear to be lying aboutefficiencycapacity factor (it's modest for a water turbine, but excellent compared to other renewable technologies -even traditional hydro) either, so it's unclear what your beef is other than you're not able to do the arithmetic required to evaluate the technology.Are they using a turbine that bears more than a passing resemblance to a Darius turbine? Yes. Is the Darius super-efficient? No. But the developer has the constraint of not blocking the water flow if the rotor locks up. Might they have bearing service issues? Maybe, but the rotor won't shut off the water. So there you go, engineering compromise. It's a low CAPEX way to get up to 100kW per genset. Just put a splice into an existing water main and go. It's one of the few small scale power generation ideas that I've seen that might really make economic sense because aside from the turbine, it looks all COTS. It's the type of energy project a small company with three principals should be - and is capable of - executing.You don't seem to understand what a bankable power project is. There is a high bar that one must clear in order to get a power purchase agreement, pass bank's engineer(s) muster, and pass the utility engineer's evaluation. Many try. Most fail. Oh and don't forget the environmental permit, construction permits, etc. Maybe this technology won't stand up over time, but clueless yahoos rarely clear all those hurdles to execute a utility power project.Lastly, if you're so good at evaluating power projects, Ian, maybe you should get off the bench and go execute a few and show us how it's done. Or at least give PG&E a ring and let them know what idiots their engineers are. I think you'll find they're well-aware that this won't replace the power they buy from Bonneville dam.Do post photos of your PPA and first-round funding agreement from your equity investors.

author: Skimask
author_rank: Super Contributor
timestamp: February 24, 2015, 05:19:34 am
content: Who are you trying to convince?Or un-convince?

author: EEVblog
author_rank: Unknown
timestamp: February 24, 2015, 05:40:46 am
content: Any energy extracted from gravity feed water pipes will lead to a reduction in dowstream pressue/flow. There isn't any free lunch here.Water authorities do this all the time to power remote sensors etc, so it is completely viable up to a certain point.

author: LabSpokane
author_rank: Super Contributor
timestamp: February 24, 2015, 06:33:33 am
content: Quote from: Skimask on February 24, 2015, 05:19:34 amI'm trying to convince you (as in the Royal "you" that enjoy bagging on energy devices for sport) that math, science and engineering matter when evaluating power generation devices, systems and projects. This "it looks bad to me, therefore it sucks" mantra is not a valid tool to weed out good from bad.I'm also trying to give you pointers on how to identify a good project versus bad. Arbitrarily crapping on a legitimate power project only commits the same error of promoting a bad power project. And if you're not willing or able to perform the simple arithmetic to determine if a project has a grain of truth to it, maybe it would be best to abstain from comment. The suggestion that the bank's engineer, the utility, the device engineer, the project engineer, the professional engineer that signed off the drawings, the equity investors and whomever else is in the chain of such a project are incompetent and can't do basic arithmetic is just silly.

author: Skimask
author_rank: Super Contributor
timestamp: February 25, 2015, 02:48:27 am
content: So, this thing requires around 3 FPS to cut-in.Assume a 36" pipe @ 3 FPS, which seems to be a sort of minimum according to the PDF.Hell, that's only ~160 GPS, 13.75 million gallons per day, ~1.8 million cu.ft. of fluid, ~5.6 acre-feet of water.How much energy could possibly be extracted from a 36" pipe flowing 3 FPS?Not a whole lot.I call it a 'pipe-dream' at best.

author: EEVblog
author_rank: Unknown
timestamp: February 25, 2015, 03:04:12 am
content: How much?

author: cosmicray
author_rank: Frequent Contributor
timestamp: February 25, 2015, 03:08:59 am
content: This feels/sounds like a solution is search of a specific problem.

author: LabSpokane
author_rank: Super Contributor
timestamp: February 25, 2015, 03:34:19 am
content: OK. Watched the video. So the price at over $10M/MWe is just completely fucking stupid. That's triple the CAPEX of the high end of small hydro at $3.6M/MWe.For reference a combined cycle natural gas turbine CAPEX runs under $1M/MWe. A biomass thermal plant goes for about $5.5M/MWe.There is so little equipment and infrastructure that these guys need to install that $10M/MWe is absolute robbery. I have no idea how they got that through. Sorry for giving you guys so much shit. This equipment should really run under $1M per MWe. There's just nothing to it.Reference source:http://www.worldenergy.org/wp-content/uploads/2013/09/WEC_J1143_CostofTECHNOLOGIES_021013_WEB_Final.pdfOh, and where they are shown installing them is utterly stupid. I am baffled as to why they are burying this stuff in the city when the western slopes of Mt Hood is the obvious location.Mea culpa. Mea culpa! It's as fucked up as a bad power project can be.

author: Skimask
author_rank: Super Contributor
timestamp: February 25, 2015, 03:58:01 am
content: Quote from: LabSpokane on February 25, 2015, 03:34:19 amThe tree-hugging fruit cakes of the world would go apeshit.

author: Lukas
author_rank: Frequent Contributor
timestamp: February 25, 2015, 05:00:36 am
content: Quote from: SeanB on February 23, 2015, 06:18:27 pmhttp://ludens.cl/paradise/paradise.html

author: mtdoc
author_rank: Super Contributor
timestamp: February 25, 2015, 06:21:43 am
content: Quote from: Lukas on February 25, 2015, 05:00:36 amThanks for the link! That is an awesome microhydro system. 2.3 - 8 kW output is huge! You could fly to the moon on that amount of powerWhen I put my own very small system in I'll be happy if I get 300 watts out of it consistently during the wet months. Still, that's 7.2 kWh per day - enough to run our home if needed. My current PV system puts out 10-20 kWh on most non winter days.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 25, 2015, 11:49:08 pm
content: Just to fan the flames, I will point out that regulatory influences and scope of analysis can change the economics of a particular energy source.For example, there are quite a few places that still have unmetered water supplies. Thinking locally, that is a virtually unlimited flow of water at 30-90 psi head. A household hydraulic motor or turbine dumping water into the sewers could extract energy from this flow with no incremental costs. From a system view it is dumb. From an ethics point of view it stinks, it adds to pumping and water production costs for the other users of the system. But it provides a benefit on an individual basis.I do suspect that if this was widely or heavily exploited the loophole would disappear rapidly.

author: mtdoc
author_rank: Super Contributor
timestamp: February 26, 2015, 01:23:19 am
content: Quote from: CatalinaWOW on February 25, 2015, 11:49:08 pm"Good points but..Just because a water connection is "unmetered"- does not mean it is unmonitored. Sudden large increases in flow would likely be noticed. That is how systems are monitored for leaks. I know because I am on the board that manages our small (35 home) state regulated water system. We do not charge by use but monitor use nevertheless to catch leaks. We have been doing this for many years and now the WA state Department of Ecology mandates water conservation measures including a system for monitoring for leaks.A typical residential water system with say 60psi (equivalent to 138 ft of head) would use 10 gallons per minute or14,400 gallons per day !just to produce a very modest 3.3kWh a day. If you're on a water system you likely also have grid power - so would it really be worth it to save less than a dollar a day on electricity?138 ft. × 10 gpm ÷ 10 derate = 138 W × 24 hrs.= 3,312 Wh per day

author: miguelvp
author_rank: Super Contributor
timestamp: February 26, 2015, 02:31:20 am
content: Use it only for the water spent that doesn't require high pressure? Like filling up the tub for a bath? or the toilet tank?

author: cdev
author_rank: Super Contributor
timestamp: March 27, 2015, 07:54:46 pm
content: I have a friend that I have not seen in a long time who lives on a property that has a year round stream and she and her husband have done exactly that, they have a Pelton wheel, which is a wheel made out of cast metal with perhaps a dozen cups to catch a strongly propelled stream of water (coming out of a nozzle) It works as advertised, and last i saw it, they were getting maybe 200 watts out of it. for maintenance, basically it uses nylon stockings to filter the water, so the stockings have to be replaced periodically. And you have to oil it once in a while. They have a 12 volt home, and they run LED lighting, a refrigerator that opens on top (more efficient) a boom box type stereo, a laptop computer..They have a big pond (maybe 100 x 100 feet) that fills with water in the rainy season (I hope its not dried out now, it probably is..)It didn't feel like they were roughing it.I hope they are okay now. California is going through a major drought.

author: benbradley
author_rank: Contributor
timestamp: January 19, 2019, 10:37:34 pm
content: I hope necroposting isn't too frowned on here, but ...This is the sort of thing that "keeps on giving," but in the wrong way - the idea is too easily misunderstood, and promoted by well-meaning people all over the Internet. I STILL see this (several "news" articles along with the Youtube video in #21) and similar stories on Lucid Energy (whether using the company's name or not) posted on Facebook, and the comments are NOT about whether gravity feed works to generate electric power (it obviously does, just like hydroelectric dams everywhere), but people DO NOT notice or understand the "gravity feed" part and think it should work in ANY city, regardless of the source of water. It's really the common interpretation of this thing that's become a scam.This recent (four months ago) post on Upworthy is arguably part of the problem - it's one of probably many "feel good" places where this sort of thing gets posted online:https://www.upworthy.com/portland-now-generates-electricity-from-turbines-installed-in-city-water-pipesThe only mention of how it actually works is about eight paragraphs into the story, near the end:"Fast Company points out that, in order to be cost and energy effective, Portland’s new power generators must be installed in pipes where water flows downhill, without having to be pumped, as the energy necessary to pump the water would negate the subsequent energy gleaned."There's no mention, stated or implied, of these pumps needing to be gravity fed up to this point. I doubt many of the people who post about this thing understand the concept even if they've read that far.But wait, there's more - read (if you dare) the Youtube comments!https://www.youtube.com/watch?time_continue=8&v=Vpubi1GjoBE

author: cdev
author_rank: Super Contributor
timestamp: January 19, 2019, 11:34:31 pm
content: just a thought.Hydro power is likely theleast sketchy form of energythere is because its clearly the oldest, its been used by humans in various forms forthousands of years.Also as somebody who has spent time in the Northwest and Northern California, there are lots of experts on independent power generation methods there because they are widely used. Very widely used. Its not pie in the sky at all, its how people run their appliances. Before PV got big there was small hydro.People who live off the main roads have small hydro setups wherever they can manage them. You can see the ponds along every creek on Google Earth, almost every one has a small hydro setup.Its a known quantity.Likewise, on the East Coast, before there was electricity, industry in the US got its start- Towns sprung up around mills, that had available sources of water power.The falling water was 'free energy', the kind you can bank on.As long as there is water in the river.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 20, 2019, 01:59:41 am
content: But even this least sketchy form of energy has it's faults. Hydropower is blamed for the end of several salmon runs and the extinction of dominant fish species in the Colorado river system. Many hydropower plants are now being decommissioned in attempts to reverse their ecological effects.TANSTAAFL

author: coppice
author_rank: Super Contributor
timestamp: January 20, 2019, 02:03:23 am
content: Quote from: CatalinaWOW on January 20, 2019, 01:59:41 amNew schemes usually have arrangements to let wildllife pass through, and to allow annual flushing, so nutrients from upstream can reach downstream farmland. The flushing also avoids the reservoirs silting up, which has been a big problem with a lot of early schemes.

author: cdev
author_rank: Super Contributor
timestamp: January 20, 2019, 02:16:36 am
content: A few years ago they discovered submerged forests of trees on the bottoms of lakes in the high Sierra, since then they've realized that several times in prehistory recent enough for the trees to still be there there have been extended droughts far longer than anything we've seen since the European colonization of the New World.So, trees grew on the bottoms of where today there are huge lakes. They dated the most recent batch at around 900-1000 years ago using dendrochronology, but there are older trees too.

author: SparkyFX
author_rank: Frequent Contributor
timestamp: February 28, 2019, 07:13:10 am
content: Quote from: CatalinaWOW on January 20, 2019, 01:59:41 amOver here there are several ship locks in the river, they each have a fish ladder because of that.But back to the hydro power generation:To accomodate larger loads, there are evenPumped hydroelectric energy storagefacilities, which seem to be cost effective just because they buffer high amounts of energy and even out the swings in use or generation. It is a simple calculation if it is reasonable to switch on additional gas turbines or open the valves on the buffers. Can´t be built everywhere, obviously.Anyway, coupling power generation to the flow of residential water sounds a bit strange, however i would not say there are no cases in which it could be practical - the mentioned examples of excess head and a high continuous flow might use it well. Would be interesting to see how water and electricity use correlates.

author: Circlotron
author_rank: Super Contributor
timestamp: June 13, 2019, 12:57:10 am
content: Quote from: T3sl4co1l on February 24, 2015, 01:02:05 amIf you had an inactive volcano caldera it might be useful. Especially for hydro power.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 13, 2019, 06:12:51 am
content: Back in the day when quite a few small towns in Oz had piped water but no electricity supply, a device was available to take the place of electric food mixers.This device coupled to the water tap (faucet)) & had a small turbine inside, which spun the mixer attachments.The down sides were that it wasted water, & there was already a device which could do that job-------Mum!There were "workarounds" for the functions done by various electrical appliances, such as "kerosene" refrigerators & clothes irons which burnt petrol (actually unleaded petrol -- sometimes called "range fuel").These were quite widely used, unlike the water tap mxer.