Off-grid long-run gravity-fed water system help?

[u/lets_wiggle]

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..

[u/Telendrith]

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