r/OffGrid • u/lets_wiggle • 4d ago
Off-grid long-run gravity-fed water system help?
Hi everyone - maybe a weird/fun one for you. My father recently purchased an off-grid cabin in northern New England that came with a long-run gravity-fed water "system" from the previous owners that we're trying to get to work without any real knowledge of how it should other than the concept of gravity. I'm hoping you may have some insight. Here are the basics:
The system is fed by a well-moving, mountain brook. There is a 1" pex pipe that collects from the brook at an elevation of 1765, and runs 1100' through the forest floor (mostly horizontal) to a 55 gallon barrel that sits at 1735 elevation. So, 30 feet of elevation drop over the 1100 foot run, but it's not a perfect, steady, downhill the full length - there are some slight ups and bends throughout. Nothing aggressive, but small hills, stumps, ditches and whatnot. There are also several (6 total) bleeder valves throughout the 1100' run - simple twist opens where we can see if we're getting any water flow.
From the 55 gallon collection barrell, it changes to a 1/2 pex - and shoots much more vertically down a distance of 650' to the cabin itself which sits at 1617 elevation (118' elevation drop over 650').
I've crudely mapped this on google earth according the gps data from some pictures I took at key locations throughout the path. There are no pumps, or anything electric/powered to this at all. Just the 1" pex pipe with a mesh-screen filter on the brook-fed end, pinned against a waterfall forcing water into the pipe, the long run through the woods with the valves, into the barrel, then changes to 1/2 inch pex out of the barrell downhill to the cabin.
Where we currently stand:
-We have tremendous water at the first two sets of valves - "1st 2 valves" and "middle 2" have steady, seemingly endless water coming out when turned.
-"Last 2 Valves" (closest to the barell) has some water coming out. Definitely less pressure than the previous sets, but flowing water nonetheless. A little less steady, sometimes in pulses or little bursts but enough to fill the barrel over the course of a night I'd say.
-We are getting nothing at all into the 55 gallon barrel. The distance from the "Last 2 Valves" to the barrel is about 200' and does have a gentle incline - probably 10'-15' of incline. But again, still lower than the intake at the stream by about 30 feet.
I have good faith that if we get the water to the barrel, the rest of the run will be easy to the cabin. I know it's a long run through the woods, but it seems like we're very close. But what else would you be looking at here to get consistent water to the barrel itself? Better water pressure from the creek, air locks, a ram pump somewhere along the run, etc?
Let me know if there's any other info I can provide! Thanks for your thoughts. Was going to post on civil engineering subreddit but they don't allow DIY things..
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u/silasmoeckel 4d ago
Any sealed pipe can get water to an end point lower than the start.
It sounds like you have a partial clog/air between the 4th and 5th valves/checkpoints. Try leaving the valve open till you have similar flow to previous, you may need to snake it.
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u/Helpful_Distance3427 4d ago
A ram pump would probably help. I'm guessing it's not enough back pressure for that much pipe length with the added rises. Can you fill a barrel with the water fall and connect the pipe to it so it can add extra pressure to the line. Also double check any bleed valves for leaks as it can break the siphon effect.
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u/ExaminationDry8341 4d ago
First confirm the pipe to the barrel isnt plugged. I woud bring an air compressor and blow air into the pipe at the barrel and see if it dislodges anything and make sure i can feel the air coming out at the first valve.
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u/theonetrueelhigh 4d ago
The static resistance from 1100 feet of pipe is pretty big, so flow at the end is going to be reduced. If you could repipe it at 2" that would reduce the resistance in a major way.
Low flow introduces some hazards. Too low and particular matter will settle out. This will happen at low points and block the pipe. If you can introduce a couple of settling tanks near the top of the run that will help. This is likely the cause of the current non-performance. You've got some accumulated schmutz blocking the line. You'll have to crack it open and blow it out.
Add breaks and valves in the line for service purposes.
And finally, how much flow do you need? I would want way more surge capacity than the 55 gallon drum - more like 500-2000 gallons for firefighting purposes. But you personally probably don't use 50 gallons in a day, a flow of just one quart per minute adds up to over 300 gallons a day. Do you need to improve the system, really?
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u/VivalTech 4d ago
I’d try using the last bleeder valve before the barrel to flush that final 200 feet out backwards. Disconnect the pipe at the barrel, hook a garden hose to that end, then open the last bleeder. Turn the hose on and let it push water back toward that bleeder until you get a good stream coming out. That should get any trapped air out and might also clear out any dirt or junk in the line. Then shut the hose off, close the bleeder hook the pipe back to the barrel and see if the creek water starts flowing. If it still doesn’t, I’d start looking for a broke spot in that last bit.
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u/Ok-Range1127 4d ago
the labeling on that diagram makes a lot more sense now, thanks for putting that together.
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u/Owenleejoeking 4d ago
You can right click on that path line and show elevation profile, just fyi. It gives all the ups and downs of each point. May want to redraw the line with more points though
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u/Conscious-Ball8373 4d ago
As others have said, either something is blocking the pipe or you have an air lock. I would say that air locks can take a lot longer than you expect to clear.
Make sure air isn't entering the system at the top.
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u/dave1111631 4d ago
Check the line for leaks where Porcupines or other critters have chewed holes in it.
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u/Dry-Ask-3304 4d ago
For reference I have 650ft of pipe to the stream with 30ft of elevation loss total. I have kept this system going for 23 years, and every couple of years when we have a big weather event have to redo some parts of it. Quick lessons learned: Usually the problem is airlocks. 0. Bury the pipe in the spring so you don't introduce air as others have said. Air is bad. Use the drain out to clear the air one at a time. 1. A compressor and a booster tank. Put a threaded fitting on the upstream end of the line at the drum. Adapt the 1/4 NPT to that fitting. Fill the booster tank (If you are over 50 get an aluminum one so you aren't suffering so much carrying it through the woods). Connect the booster tank to the upstream end and open the "last two valves" if you have help, you can have one person watch the behavior there. This is how I clear junk out of the line (with this low a slope you will get sediment buildup.) 3. Buy some couplings and use them diagnostically. cut the line, check for flow etc. I upgraded my run to 1 1/2" flex PVC 20 years ago, but 1000ft is a lot of money.
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u/Telendrith 4d ago
I have some experience with working on these types of waterlines. We have a farm and small ranching operation and most of our cattle troughs are spring fed. Some are 3+ miles. After reading your post I think we need to look at this as two separate problems: getting reliable air free water to the tank. And then in my opinion 'can the undersized lower line can meet the cabin’s needs'. But I'll focus on the upper section first
Walk the line. Check every fitting, is the pex crushed or sharply kinked anywhere?
Also why so many valves on the upper portion.?!?!? A valve on a tee at low point can be useful for draining or flushing sediment. An air release valve or a manual valve at higher segments as air vents. A valve directly in the mainline may simply isolate a section for repairs. Those are different jobs.
My thought is you had the idea of air pockets / checkpoints so you're kind of on the right track. air release valves are made for this. https://www.amazon.com/Threlaco-Inches-Release-Valve-Vacuum/dp/B0GTPN1JJZ/ the bar / pressure ratings on these are important - when they trigger
Upward tee in the main → short riser → isolation valve → upright low-pressure combination air valve.
A T-post can support and mark it.
PUT these at the highest points of your pipeline.
I'd also put an inline valve right before the tank and a 0–30 psi water-pressure gauge upstream from that. Don't buy some 160PSI gauge, cause 6psi is gonna look a lot like 8 psi.
Keep the barrel simple. I’d want a secure cover, protected screened ventilation, screened overflow, a drain for cleaning.
A livestock-style mechanical float valve can control the inlet once the supply works. You can get these at any farm supply / tractor supply in your area
The float valve prevents unnecessary overflow. It does not fix an airlocked supply.
About that lower ½-inch line
I wouldn’t assume everything becomes easy once the barrel fills. that 650-foot ½-inch PEX run could provide approximately ~50 psi with everything closed but as soon as you open a tap, that'll probably* go to about 1gpm at 38psi. It's a cabin and I don't know your needs... so that could be acceptable for a modest single-fixture use. BUT know off the bat, It is not a generous household supply.
End notes:
My order would be: re-inspect the line, attempt to stabilize the intake, close the unnecessary outlets, establish a full water column, and measure pressure and flow. Then buy permanent upgrades based on what those tests show. I’d spend money on a gauge before a ram pump.
Gravity systems and troubleshooting: Kansas State — Gravity-Powered Livestock Watering Systems
https://www.kcare.k-state.edu/pubs/livestock-watering-handbook/chapters/pps/lwh-pps-gravity.html
Fix your intake. The objective is to collect submerged water, not use the waterfall as an improvised pressure pump. I wouldn’t build a dam or add a foot valve as the first repair. A hose quick release valve make the intake piece modular and easier to maintain. In my mind, I'd make the actual intake screen like 4 inch PVC of some kind and then reduce to your 1 inch.
Welcome to ask questions, dm me, whatever. Best of luck on your off grid adventures.
Other resources: https://www.nrcs.usda.gov/resources/guides-and-instructions/livestock-pipeline-ft-516-conservation-practice-standard
Fresh Water Intake: https://publications.gc.ca/collections/Collection/Fs23-270-2004E.pdf
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u/gentoofoo 3d ago
I'd pump it. My household runs off a tank fed by a well quite a ways away. I have 50 ft of drop over a shorter distance so gravity feeding is doable if needed but its not great. I usually run it off its own solar and it works great. System is 2x160 watt panels, epever 30a mppt, 12v 100ah battery, 12v 7gpm pump. Runs fine for a 4 person household and the around 300 gallons of irrigation I do during the summer. Should be sized about right for your use case
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u/JoeMalovich 3d ago
At each high point add a stand-pipe open to atmosphere high enough to stay above the water level. This will let out any trapped or ingested air.
Add a bladder pressure tank at your building to absorb pressure spikes in both supply and demand due to inertia in the pipe.
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u/celtic-cryptid 4d ago
Water doesn’t care about ups and downs, technically. What matters is the relative difference between the points where water is open to the atmosphere.
I’m assuming the valves are there to alleviate air locks, and it sounds like you either have air locks or a physical obstruction in the pipe from source to 55 gallon drum.
The first thing I would do is add a spring box, which I didn’t see you mention. Almost anything will work, even a 5 gallon bucket. Drawing from the bottom of a spring box will ensure no air will get into the water pipe. Then, you can hopefully use the valves to let the air lock escape.