04-22-09, 07:57 AM | #11 |
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What you've described, wyatt, is an auto-fill device. What I don't like about it, is that now you're introducing the nasty hard city/ground water into your wonderfully soft rainwater system.
A big issue I've run across is back pressure and back siphoning from a "cross connected" system (I'm learning the lingo!) If the city water supply loses pressure, there can be no chance of the non-potable water from being forced by pressure, or sucked in by siphon action, into the potable water supply. I think a toilet already does this, as the valve in the tank dispenses above the water level in the tank. But we need to mix the two sources before it gets to the toilet fill valve... ...The research continues.
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04-22-09, 11:48 AM | #12 |
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hmmm... good thing you are telling me why these things are a bad idea... let's try this one...
ok, so we have a cistern, a tank in the attic, and a house. Nothing is to scale, PLEASE do calculations if you are going to do something like this, there are probably easier ways to accomplish the same thing, I am not qualified to design these sorts of systems, etc. etc. etc. Latest idea: IF cistern is over 50% full, pump 1 operates every time valve 1 is tripped, topping off the tank IF the cistern is less than 50% full, pump 1 no longer operates, pump 2 AND city water operate every time valve 2 - city valve are tripped, mixing 50/50 and filling the tank (More likely there would be one valve tripped that started both) IF the cistern is dry (or below a certain level), pump 1 and pump 2 no longer operate, city water operates every time city valve (or common valve) is tripped, filling the tank IF you get tired of my ideas, just let me know. Have a good Earth Day! Wyatt Last edited by wyatt; 04-25-09 at 07:48 PM.. |
04-22-09, 02:57 PM | #13 |
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Why would I get tired of your ideas? That's why I posted here!
We could eliminate pump 1 and use a simple logic program to mix the two sources into the attic tank. Would need a level transducer in the cistern, then. The attic tank would have 8 or 9 feet of head, giving us 2.5 to 2.8 PSI to the toilet. Wonder if that would be enough to operate the toilet fill valve...
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04-22-09, 03:11 PM | #14 |
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I think so, since the toilet starts to fill the instant you flush and doesn't stop until the toilet is full. That binary ON/OFF type thing isn't operated by the pressure of the water if I understand correctly, it's operated by water level in the tank. If I have a few extra pieces laying around I will test out the gravity feed portion, but I will be testing it on the counter next to the toilet first, because if it works there, it will for sure work in the attic. It's possible you will have a thumbs up or thumbs down tomorrow on the gravity feed, but it seems a simple siphon action would fill the tank.
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04-22-09, 09:01 PM | #15 |
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I proved two things, and disproved one!
Experiment: Attach a siphon hose to the tank inlet, see if gravity feed will fill the tank. Hypothesis: Yes, it will. Method: No siphon hose available... no hose available... made a hose out of plastic, duct taping the seam, duct tape the "hose" to an old tank fitting. Fill "hose" with water until the tank starts to fill. Outcome: Tank didn't fill, even when water was one foot over the rim. Dis-proved hypothesis! Proved that "hose" didn't hold water well (leaked like crazy) Proved that the tank required pressure to activate. How much pressure is unclear. I was hoping I could get video of it working... no such luck. The tank actuator (at least mine) is pressure activated. A better experiment with better quality components would be needed to determine if a gravity feed system would be able to fill a toilet tank. Sorry, I guess I have to leave that one up to you. |
04-23-09, 07:32 AM | #16 |
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Ha ha! you kill me, wyatt! You've officially done more hands-on work than I have with this project! I'm still stuck in my cubicle researching plumbing codes, since we don't know what we don't know at this point.
Our resident construction guy has constructed a mock-up for testing, though; I think he's going to set the toilet today and plumb up the drain. Today I've got to work up a Preliminary Report for the client, who is coming for a visit next week.
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04-25-09, 07:50 PM | #17 |
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any sweet updates? can you trip the toilet with pressure from the attic? video? I've thought more about your project than I have about most of mine!
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04-29-09, 11:33 AM | #18 |
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No big updates yet.
The client liked my report and our mock-up, so work will continue. Still researching plumbing codes and trying to wrap my head around backflow prevention valves.
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05-06-09, 10:30 AM | #19 |
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I wanted to post some rough schematics that I've sketched up to show what I've been coming up with, but since this is a paying customer's project, I probably shouldn't. Non-disclosure statements and all that jazz, you know.
"It's all very 'hush-hush' and 'hoosh-hoosh', you know" (Terry Thomas as Lt. Col. Hawthorne in "It's a Mad Mad Mad Mad World") Three different ideas; One: Collected rainwater is pumped from a cistern to a small tank in the house (not the attic, due to possibility of freezing). Then gravity fed to a valve that would mix the city and rainwater roughly 2:1 as it goes to the toilet. An RP backflow preventer would be needed on the city water supply line to prevent the possibility of rainwater contaminating it. And they ain't cheap. Two: Rainwater pumped into a small interior tank as before, but topped off with city water when rainwater is depleted. An airgap (cheap!) at the top of the small tank would prevent backflow/backsiphon. Another pump in the small tank would provide pressure to operate the toilet. Is a second pump cheaper than an RP device? Three: Junk the small tank altogether and pump the rainwater straight from the cistern to a solenoid-actuated valve that chooses between city water or rainwater, depending on availability of rainwater. Also requires an RP device on the city water supply line. Hopefully this is sufficiently detailed to get the conceptual idea across, without disclosing too much to get me in trouble.
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05-28-09, 03:51 PM | #20 |
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This week I finally got around to doing some hands-on testing. I rigged our mock up to a garden hose and recorded some tank refill times at various pressures. The garden hose gave me around 46 psi static, 40ish while filling. That took about 33 seconds to refill the tank. I got down to 10 psi, and that took about a minute and ten seconds.
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collection, harvesting, rain, water |
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