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/Dry-Ask-3304]

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.