So how can this not work

So what are the problems with this ?

So long as it rains enough should work good

Ill go. That cow wouldve been pretty thirsty the last 2 years around here

Well, the water catch barrel does not have the capacity to keep the tank full, unless you have a very wet climate. A bigger storage tank would be more better.

If possible I would have a back up water supply.

You can easily stack caged IBC Totes, so that they flow into each other and retain more water.

Keith

Filtration, particularly if leaves are anywhere nearby. Depending on roof material possible heavy metal issues, thinking lead boots but possible others.

Next capacity. Ideally you want to catch and hold every drop. Square footage would be important as well. And of course balanced against demand.

Like others have said have a ready back up source as nothing is ever perfectly balanced.

And if storing longterm some measure to keep it potable and not breeding nasties like mosquitos.

You’re one invention away from windshield wipers on a goat’s behind. Keep after it!!!
Seriously, looks sound to me!

I mean when humans have rain water system's the most important part is filtration, but it depends on what birds you've got in the area I guess.

We use 1500 gallon tanks at the end of each side of the barns. Bury a freeze proof hydrant with 1" PVC coming out of the bulkhead. Use panels to enclose the exposed pipe and cover with a minimum of three feet of used straw. I will take pictures over the weekend of the different types we have installed.

That cow is about to turn 180 degrees and take a dump in that thing.

My thoughts
1 You need to protect the holding tank and the piping to the watering tank or the cattle will destroy it quickly
2. As stated the roof collection area may not be large enough to keep enough water in the tank. Even beef cows will dring 15-20 gallons per day, more when hotter
3. You many need to have a taller holding tank and keep it full to have the head pressure you need to supply the tank.
4. During the warm season the water coming off the roof will be warmed and you may grow a lot of algae and scum in both the holding tank and the watering tank.
You can buy plastic tanks with bottom valves to empty. If it were me I would mount one on a wagon or trailer and fill it and take it out to the site and you can have the gutter to collect rainfall as well. This will give you more head pressure, capacity and still be mobile. If water gets bad animals drink less thus eat less and gain slower.

Bryce

Storage tank needs to be elevated to the point that the bottom of it is close to the level of where the float in the stock tank is. Set up on blocks or something. Otherwise you're only using, from the looks of it, about half the capacity of the storage tank. Water won't run uphill.

A cover on the gutter would keep leaves out of the tank.

Problem need a bigger storage barrel. people underestimate how much water a roof catches in a good rain . A 50x20 roof(1000sq ft) will get 300 gallons on a half inch rain.

That valve, will it be able to close with the weight of that water in the barrel? It’ll need a longer arm and the cow will screw with it.
Looks like a the guy who drew it is onto something anyways.

As previously noted, as shown, only part of the water in the barrel would flow to the tank. Once the water levels are equal, valve would stay open and water levels in barrel and tank would drop to level of the connecting pipe, then livestock would drain the tank dry. So bigger tank and connector lower.....maybe underground.

General concept is not new. Many farm houses had a cistern.....a big underground tank......that was used to catch rain water off roofs. Many of those even used for drinking water. Pulled up by a hand pump. Used in place of, or in addition to, a dug well.

Have thought the concept could also be used in all homes, catching rain water to be used for flushing toilets, watering plants, gardens and such. Tank would have to be big and tall, but concept is doable.

Aside from collecting rain water, general process is no different than any public water system that uses water towers and stand pipes. They are all gravity fed. Water is only pumped into the tower.

A farm pond with pipe thru the dam and tank below is the same, except the pond is bigger than the barrel. BEST of those I've ever seen has a long but skinny tank mostly buried in the pond dam, with only a very small area exposed for animals to drink from. Being buried deep, water in the tank rarely, if ever, freezes.

Big problem with cisterns is bacteria. When my grandparents passed away and my parents got the house, Mom had the water twawrsd and it was not good. We scrubbed and disinfected the walls and floors and still no good at least according to the lab. Course they loved in that house for 50+ years so it couldn't of been that bad.

That set up would be dry in One day
Cattle drink a lot

This is a problem. I can see mad cow disease happening. Once you get a cow mad its hard to cure it.

I'm with Osagan elevate the tank. I also agree with the bigger storage capacity guys and Bryce in regards to protecting it. Cattle like to rub and scratch on anything you build.

When I first got divorced I lived in a bunkhouse that was fed water off of the covered arena. All the stalls and stock tanks were fed from it too as it had about 6000 sf of roof.

This is the first one. The top is open. With no trees around, didn't worry about leaves.

IMHO: Nice idea.
I agree with the gutter screen idea.
You would need to raise the barrel so the outlet is level with the desired tank level and add a 2nd, 1 IBC tank is double the capacity of 2 barrels.
Raise the fill level inlet as high as you can to maximize volume.
Maybe put some minnows in the tank for fishing, and mosquito control.

Have to drain the tank when the temp goes below 10. Hydrants run in front of the barn.

Sump pump in bottom connected to switch above hydrant. PEX piping to each individual stall with shutoff valve to control.

When I was kicking this idea around for use in a home..........in addition to the leaves, it occurred to me that gutters would also carry dust off the roof and gutter. So I thought it might help to use a sediment trap in the downspout. A foot or so below the gutter, put in a big T fitting. In the straight line below the T, start putting in a series of reducers, so final drain would be 3/4 inch or so. First flush off the roof and out the gutter with dust would flow down into the sediment trap. But necked down like that, would quickly back up to the T, then take alternate, wide open big pipe down to the storage tank. The sediment trap would be self flushing.

There are a lot of video;s on water storage , off roofs . On off grid and cottage forums .With drawings. Also depends how low your temps get. Frozen water bowls are common. old243

I've toured a few antebellum big houses that had such systems. One memorable one is the Jemison House in Tuscaloosa that was barely completed before the war broke out. It had indoor running water for flushing toilets and bath tub.

Roof catch to in ground cistern. Servant powered hand pump to in attic tank for indoor plumbing. State of the art for the time.