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Seth
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# Posted: 19 Sep 2013 06:10pm
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Hey guys,
At this property in Costa Rica where I'll be building my cabin I have a somewhat interesting water issue and could use some people's thoughts on it. It's really a physics-of-water question. If anyone's willing to think about this for a few minutes and comment, I'd greatly appreciate it.
I'm providing an image to help illustrate the issue.
So - The village's water supply is large concrete box on the property behind and uphill from mine (blue box in photo). It's fed by tubes running from springs up in the mountains. From the box, a tube goes downhill along the public road and into the village, where it's dispersed among the houses (blue arrow and rectangle). Everybody down in the village has good water pressure and very rare shortages.
With my site (the orange box) being uphill from most of the other houses, I've been struggling to decide how to deal with water. The little local water committee first said that I could only get a tube coming back up hill from down in the village (coming up the black arrows). We connected a tube to my neighbor down the hill and ran it most of the way up my property and found that although water would arrive that way, it didn't have much pressure at all. Obviously, in that instance, if there was a shortage I would be the first one without water.
So I started wondering about the possibility of getting water from that main tube going down into the village (the blue arrow pointing downhill). At first the water committee said they couldn't do it because the line (the white arrow) would have to go through my neighbor's property. But then I talked to my neighbor and he said he'd be totally fine with it - (they're good friends of mine).
So the question I need answered is: with all that water rushing downhill through the main tube (blue arrow) toward the village, would water actually enter and run through a tube oriented like the white arrow in this diagram?
Anybody have any thoughts?
Best,
Seth
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GomerPile
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# Posted: 19 Sep 2013 06:25pm - Edited by: GomerPile
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Pressure is the difference in feet between your faucet and the outlet of the water tank.
11.53ft = 5PSI
You will have losses in the piping which will reduce the flow rate. Longer the pipe = less flow.
Bottom line is that a more direct line will have less friction loss and will give you more water. Since your elevation is closer to the source you have less pressure to deal with compared to someone down in the village.
Here's a good page with calculators that you might find useful:
http://www.sunpumps.com/engineering/engineering.php
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Martian
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# Posted: 19 Sep 2013 06:28pm
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Your pressure is going to be determined by the "head" pressure at your elevation in relation to the tank regardless of whether it first goes down hill or not. As long as the tank has water, you will have water. The people further down the hill will always have more pressure, but you should get some flow as long as there is water in the line above you. You may have to add a pressure pump to give you the pressure you desire.
Tom
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Seth
Member
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# Posted: 19 Sep 2013 06:32pm
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Thanks guys. So Tom, am I correct in thinking that either way I'd have water but the white-arrow option is preferable?
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Seth
Member
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# Posted: 19 Sep 2013 06:41pm
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And a question for Gomer - what's a 'normal' or 'acceptable' psi for showers, sinks, etc?
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Seth
Member
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# Posted: 19 Sep 2013 06:53pm
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Makes me think that I should go for the white-arrow, more direct source, and maybe mount a 100 gallon tank fed by the white-arrow tube on a stand above the level of the shower head with outputs going to the shower, sink, and toilet. Are there any easy and non-electric setups that would automatically stop the tank being filled when it's full?
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Martian
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# Posted: 19 Sep 2013 07:05pm - Edited by: Martian
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Seth, assuming the distance isn't that much greater from the supply, it isn't going to matter a whole lot. The static pressure in the line is determined by the head pressure. Now, if the line in the village is small, then you will benefit more from the white line, but if its a large pipe, you most likely will not see any difference. Depending on the pump you are using, you might be able to draw some water from down the hill if you use the black line for supply. However, it would be temporary.
I would use a cistern tank to ensure I had water during dry periods.
Just read this:
Are there any easy and non-electric setups that would automatically stop the tank being filled when it's full?
Short answer; yes. A float valve, much like in a toilet, would do it.
Tom
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Fanman
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# Posted: 19 Sep 2013 07:25pm
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Statically (nobody using water), your water pressure will be the same either way; it's strictly a function of the elevation difference. Pipe size is irrelevant, too.
However, once people (whether it's you or the people in the village) start using water, there is a pressure drop due to friction, which will reduce your water pressure. In this case, the larger the pipe size, the less drop there will be. The white line is better either way, especially if the pipe from the tank to the tee where you connect is fairly large.
What is the elevation difference? If, for example, you're halfway up the hill from the village to the tank, your water pressure will never be more than half of what they get in the village no matter how you connect it.
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Seth
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# Posted: 19 Sep 2013 08:04pm
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I really appreciate these replies - thanks very much everybody.
Fanman: I'm not sure exactly what the elevation difference is - from my house site to the tank it's probably 15-30 ft of difference in height, but that could be wildly inaccurate. My GPS gives me very variable readings for elevation between the two spots. I'd say I'm about 3/4 of the way up the hill from the village. The village water pressure in the village is really really high. If I got 1/4 or 1/2 of their pressure, it would be sufficient. But I think just incase, I'll plan on having to have a tank on a stand to gain some pressure from gravity.
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MtnDon
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# Posted: 19 Sep 2013 08:48pm
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Quoting: Seth I'll plan on having to have a tank on a stand to gain some pressure from gravity.
0.43 PSI pressure per foot of elevation difference, ignoring frictional losses.
Many people will find less than 20 PSI too low.
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Seth
Member
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# Posted: 19 Sep 2013 08:54pm
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Quoting: MtnDon 0.43 PSI pressure per foot of elevation difference, ignoring frictional losses. Many people will find less than 20 PSI too low.
In my dry cabin in Alaska I have a 15 gallon water tank upstairs that feeds the faucet downstairs and provides enough pressure for my liking. And for bathing I've got a bucket with a cheap plastic shower head mounted on it, and those few gallons of water come out at a very acceptable pressure... so I think this kind of set-up would be peachy keen for someone like me who's used to living without much water pressure.
I'm curious about what your friend has brought down for solar stuff. I'd like to run lights and maybe a small fridge, perhaps be able to recharge a laptop or a phone - but no tv, no microwave, nothing else really. Wondering what kind of setup I could get away with and carry down there myself.
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MtnDon
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# Posted: 19 Sep 2013 10:26pm
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Small. IIRC he has a couple of 80 watt or so panels, a PWM charge controller and 2 golf cart batteries. Some cheap square wave inverter. It took a while down there to find a couple of Trojan T105RE batteries that were of recent manufacture. They are date coded at the factory. He also has a Honda generator (EU1000i ??) and a good charger as where he is there are many cloudy days.
Small refrigerators are power hogs unless they are one of the expensive ones that use the Danfoss compressor. Many are the 'Peltier effect' type and those are not only power hogs, IMO, but can not cool to any more than 40-45 degrees F below the ambient air. Regular el-cheapo dorm fridges are generally a poor idea for solar power. The Danfoss type can be used to freeze food, not just keep it frozen. There are a number of Danfoss based ones but they run $500 and up for only a couple cu ft. $1200 for 6 - 8 cu ft.. About the same as a propane fridge in the same size, here in the USA. I do not know what is commonly used in central america.
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Martian
Member
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# Posted: 19 Sep 2013 11:10pm
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If you build a well insulated fridge box, you can do quite well with the marine, air-cooled 12vdc units.
Tom
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Seth
Member
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# Posted: 19 Sep 2013 11:25pm
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Interesting - thanks. It would be great to be off the grid but the lack of available equipment down there and with electricity being as cheap as it is ($20/month for my friend's house where they watch TV all the time and have a full fridge), and given that I'll only be there half the year until I retire, maybe I'll just hop onto the grid or better yet - be sans electricity.
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Truecabin
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# Posted: 20 Sep 2013 11:24am
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from your diagram
at times when the village is using a lot of water if you open your faucet at same time you may get suction instead of water and then the village will get bubbles in their water and it will jerk and bang and spit until all the air is out. if you do the white line direct they could be mad at you
or the white has to come direct out of the tank not the pipe
if you have your own tank on a stand and a float valve to refill it from the white line that will work from the white line with no problems unless your own tank becomes empty at a peak water usage time
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PA_Bound
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# Posted: 21 Sep 2013 07:01pm
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Truecabin is right-on here, good catch!
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bldginsp
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# Posted: 22 Sep 2013 11:11am - Edited by: bldginsp
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Seth- my one comment is that if you run the line through your neighbors property and you don't have a legal easement, what happens if they sell the property and the next owner doesn't want to let you run the line across? I'd want an assurance that it will stay before I spent the money.
If the pipe up from the village is legally permanent, perhaps using it to fill a tank and then using a pump for pressure is best, just so you know your water source is more secure.
But perhaps in Costa Rica peoples' attitudes about these things are very different than in our litigious society. Maybe that's why you went to Costa Rica.
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alfa_romeo55
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# Posted: 10 Oct 2013 01:57pm
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The best thing to do Seth is to build your own tank and either run the white line or the blue line from the village and put a float valve on it. That way you always have water. If your tank runs low refill with whatever line you have run to the tank. forget about running the line directly into the house. If you want more pressure simply add a pump. However you will have to elevate your tank.
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Seth
Member
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# Posted: 10 Oct 2013 07:17pm
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All very helpful replies. Looks like I'll be mounting a 300 or so gallon tank with a float valve above the level of my kitchen and bath-house. In my dry cabin in Alaska I have just a 15-gallon tank upstairs feeding the downstairs faucet and the pressure is quite ample for the style of living I'm accustomed to. As far as going along the border of my neighbor's property, I will try to get a legally-binding agreement if it's possible, but they're one of the village's legacy families and I'm on friendly terms with all of them young and old alike. If that somehow soured and I had to, I could easily change to receive water from up the other side of the public road.
My 6 x 5 meter cabin design is coming along slowly, I'll upload a few sketches when I get to that point, hopefully soon!
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toyota_mdt_tech
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# Posted: 10 Oct 2013 09:14pm
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Quoting: Seth And a question for Gomer - what's a 'normal' or 'acceptable' psi for showers, sinks, etc?
I think right around 40 PSI max is ideal. More than that, it actually starts to wear our plumbing. It can really creak trouble. Especially in the fixtures too.
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Truecabin
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# Posted: 11 Oct 2013 03:14pm
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yes toyota 40 is normal but its around 70 or 80 that you can have trouble with appliances
washing machines dishwasher or fridge any appliance that has systems and has water controls
mostly house problems not cabin problems
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Seth
Member
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# Posted: 13 May 2014 09:42pm - Edited by: Seth
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So... back again! Happy to report I got the house built and installed a 250 gallon water tank about 2.5 meters (~8 feet) off the ground which is being fed from a spring on a neighbor's property. Water leaves the tank in a 3/4" PVC tube and splits off to 1/2 tubes from there. There is great pressure at all the PVC/plastic outlets (in the kitchen and a couple outside for hoses) but the pressure to fill the toilet after a flush and in the bathroom sink is quite low... takes about two minutes for the toilet tank to refill after a flush. Any idea why there'd be such a difference between the straight PVC outlets and those that have the toilet-connector-hose style of connection? Are they super constricted inside?
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MtnDon
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# Posted: 13 May 2014 10:44pm
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What is the pressure and flow at the shut off that connects to the toilet, assuming there is the usual shut off just below the toilet? Does water come out of there like the other faucets? If so then the toilet valve may have a designed in restriction to extend the life of the toilet valve. Have you actually measured the pressure? Theoretically the maximum pressure you can have is 0.43 PSI per foot of elevation between the upper level of the water height at the supply and the point of use.
20 PSI is low in my book, 40 PSI is normal, and higher than that unnecessary, IMO.
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Seth
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# Posted: 13 May 2014 11:19pm
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Quoting: MtnDon What is the pressure and flow at the shut off that connects to the toilet, assuming there is the usual shut off just below the toilet? Does water come out of there like the other faucets? If so then the toilet valve may have a designed in restriction to extend the life of the toilet valve. Have you actually measured the pressure? Theoretically the maximum pressure you can have is 0.43 PSI per foot of elevation between the upper level of the water height at the supply and the point of use.
At the juncture where the toilet-connector hose is attached to the water feed there is good pressure - similar to the other outlets where it's just a plastic ball valve. I didn't have a way to measure the pressure but I suspect, taking your formula into consideration, that I have pretty low pressure, say 12 psi. So perhaps it's not enough to push the toilet valve fully open?
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MtnDon
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# Posted: 13 May 2014 11:33pm
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That's it. Our toilets take a longer time to refill too as we run 30 PSI in our house because lower pressure is easier on valves in things like dishwashers and clothes washing machines.
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Seth
Member
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# Posted: 13 May 2014 11:36pm
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So there's really nothing I can do aside from putting a direct feed into the toilet tank that I'd have to turn on/off for each fill?
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MtnDon
Member
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# Posted: 14 May 2014 12:35am
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You could get into pumps and stuff... The simple thing is to just let the toilet fill slowly.
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Seth
Member
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# Posted: 14 May 2014 12:46am
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Simple sounds good to me. Thanks.
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Don_P
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# Posted: 14 May 2014 07:57am
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All depending, dirt and junk tend to collect in our flush valve. I occassionally disassemble, clean and reassemble it. If you ever hook to the town supply an anti siphon device should probably be in there... and realize that no one else has one, the supply should probably be considered contaminated. My folks were in an eastern block country that couldn't pay its' power bill and the power went off daily. The water supply then went from positive to negative pressure frequently, not a scenario for drinking water. On the far end of our county there was a small mill town with their own cobbled together water system. Being in the mountains there were some good elevation changes. Down low it could hit 300 psi. I've inadvertantly hit our camper with 90 psi by running a hose down the hill to it. Happily it held until I ran back up the hill and closed the hydrant... felt kind of like the mosquito joke "pull out Ethel, you've hit an artery  "
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