Plumbing two 2500 Gal. Water Storage Tanks together

Thanks again for the forum's advice in placing our 2 x 2,500 gallon water storage tanks.  We're prepping the area now (clearing stumps, leveling, packing gravel) to place the tanks.  Now we're sorting out the plumbing details.

The overall system (photo 1) is simple:  Rainwater gathered in IBCs at the house, pumped 150' over and 18' up to the top of the tanks via 3/4" garden hose.  We then gravity feed water from the bottom of the tanks to irrigate our orchard.

Our question:  Since repeatedly hooking the garden hose directly to the top of the tanks (filling one at a time) would probably eventually stress-out those tank inlet fittings, we're thinking to install a simple PVC water handling manifold (photo 2).  Does this design seem ok?

Four in-line valves allow us to choose which tank to fill or draw water from.  (Given our stark on-off rain patterns, we do not think we'll ever be filling our tanks at the same time as irrigating from them.)  One inlet/outlet valve at the base of the manifold permits easy, low-torque garden hose connection.  Our thought is that the four connections of the manifold to the tanks will mutually support e/o, creating a solid, reliable, long-lasting manifold.

Photo 3 shows the 8" standoff from the tanks to the plane of the manifold.  If one tank moved ever-so-slighlty over time relative to the other tank, the manifold could flex without breaking.

Seem ok?  We've never done this before, so it may well be stark raving stupid.  This very dry summer, we distributed the 2000 gallons of water from our IBCs and barrels via 5 gallon buckets.  Endless Summer, indeed.

Roy, I have plenty of experience with this situation.
I have a few points to consider;
- if you use a larger pipe [ called a rising main ] to fill the distant tanks it will be faster and use less energy, particularly over 150'
- if the pump is installed near the IBC flows will be improved also.
- Black poly pipe is ideal and the fittings are easy to use. I suggest at least 25mm pipe, if cost is important.
- use fittings at the big tank to fill one from the top, I install a 90 bend with a thread and screw the fitting into the tank side at the top.
- Do not use PVC fittings you need flexibility
- Fit ball valves to the lower part of the tank wall on each tank, then join the two tanks at the bottom with flexible pipe and flanges using say 11/2 inch pipe.
- Have that pipe long enough to install a T piece and another 11/2 inch ball valve on the T.
- That valve is where your take off for water is fitted.
So the system will work as follows, the IBC's supply the pump, which fills one tank only.
The interconnection between the tanks will ensure both tanks are filled.
The separate valves on each tank means you can isolated them for repairs.
By using 11/2 inch fittings and pipes it means if you upgrade things are in place and it minimises blockages.
Also, if you fitted a submersible pump it would automatically shift the water without you needing to be present.
And if the IBC's were all connected to work as a single tank it may be easier to manage.

Thanks John!  Being both elegant and proven, I'll do exactly as you suggest.  Compared to the problematic IBC end of the system, these larger tanks should be much easier to manage.

In the rainy season, I spend lots of early mornings and late nights shifting water around the collection tanks, as one IBC can easily fill in a few hours of heavy rain, and I do not have an overflow system (yet).  The IBCs are stacked, so connecting them into one common volume is tricky.  But I'll keep staring at them.

I'll also ponder an automatic submersible pump while I get a feel for manual operation, but it is an attractive idea.

The giant stump blocking the tractor's way to the storage tank area has been defeated.  Well, it was closer to a tie, but we eventually pieced it out, three chainsaw chains later.  The two tanks wait patiently in the background.

Its great that you are keen to try my ideas,I have made many mistakes getting to the position I am now in.
Its nice to jump the mistakes!
I use a submersible pump in a 1000 gal tank and transfer it to the 5000 gal tank during storms, its great to hear it kick in, knowing that's another lot of water stored.
If the IBC's are linked in the layers maybe just link each layer together.

I take it the new tanks will not fit in the area where the IBC's are?
That would make things really easy.

Thanks again, John.  We just ordered all the black poly fixins, including 200' of 1" ID black poly tubing, from Drip Depot.  The "Perma-Loc" connectors look fun to work with and very reasonably priced.  Since we'll be back at it in the spring designing the irrigation side, this was a very useful exercise in getting to know their products and website.  These parts will get rainwater from the IBCs to the tanks, 1" the whole way, exactly like you described.  We need another supplier for the output ball valves, but one thing at a time.

We're leaning toward your solution on the collection side also -- a single 1000 gallon collection tank with a float switch to automatically start our transfer pump (though we as yet have no idea what will then automatically stop it).  The space on that end of the house is limited by our electric service, chimney, and a doorway.  2 x 2,500 gallon tanks would take over that entire side of the house.  Plus, the house is 3/4 of the way down our hillside lot.  We prefer to have the storage tanks at the top of the hill for gravity-fed irrigation.

Roy, the float switch operates both on and off.
It has a mercury switch inside the loose end that floats around.
If the water level is low the float drops down and the mercury inside the switch moves to one end and disconnects the electrical circuit, hence the pump stops.

You're aces John, thanks for the ideas and inspiration.  Your suggestions sometimes hibernate by day, but then tiptoe around my brain at night, rearranging the furniture.

My wife and I leveled a pad for one storage tank yesterday afternoon, but World Series baseball first-pitch fortuitously stalled our digging of the second tank pad.  Fortuitous, because...

Connecting the dots of your ideas, I awoke this a.m. thinking duh, install one 2,500 gallon tank for collection behind the house (I can't fit two there, but I probably could fit one), then the other 2,500 gallon tank on the hill (in the spot we just leveled) to source gravity-fed irrigation.  No joining tanks, no float valves, and no wandering around in my undies at night in the rain tapping IBCs trying to divine water levels and time-to-overflow.  2,500 gallons of collection volume buys a whole lotta forgiveness.  

So the black poly rising main transfer system will work exactly as you suggested (parts arriving tomorrow).  We'll install and plumb the single storage tank on the hill, transfer water to it from our 5 already-full collection IBCs so they can refill, then begin staring at our gutters to design a new flow for the single 2,500 gallon collection tank.

Storage system  getting closer.  My wife and I finished the landscape timber barrier for the tank pad this morning (photo).  We used lumber we milled from a tree downed not 20' from this pad site, so it kinda poetic.  Treated the 7" timbers  with 1-2 layers of "Copper Green" preservative, half-lapped the corner joints with a chainsaw then secured them with 6" Timber Loc lag bolts.  Time to tamp and fill with pea gravel.

Our Drip Depot order just arrived with 200' of horribly kinked 1" black poly tubing.  Unusable, so that will stall the project at least a week. We'll let Permies know how Drip Depot handles the return, so we'll all know if they're a company deserving of our business.

Just a brief follow-up:  Drip Depot did quickly fix their error.  They apologized and overnighted the replacement tubing free of charge, plus couplers to utilize the original kinked tubing.  I plan to stick with them for the irrigation-side installation.

Packed 1-1/2 yards of 5/8" crusher stone into the tank pad yesterday.  That's one of the few jobs best done in the rain, as it helped settle the binder.  Time to move the tank into place and install all this fancy plumbing!

To complete the story...

We moved the tank into position yesterday.  We initially tried just a 25' choke strap 2/3 up the tank, using the tractor with only one fork tine, inverted (max height) to raise the tank.  At max extension, we only got the tank about 6" off the ground, not high enough to maneuver our somewhat uneven property.

So plan B was a sheet of 3/4" plywood screwed to a standard pallet.  We used the choke strap to raise one side pf the tank to place the plywood/pallet underneath, then used a ratchet strap to secure the tank higher up (attaching to the top of the tractor's front guard).  Photo 1.

To get the tank off without disturbing our meticulously leveled and packed gravel, we reversed the strap to the other side and used our Polaris to anchor the tank while we backed the tractor up. Photo 2.

Worked like a charm.  Today the plumbing goes in.

Up and running! (photo 1)

Plumbed just like you said, John.  1" black poly tubing, especially with those Perma-Loc fittings, is magical.  The only leak I had was in a press-fit to a barb, which I quickly solved with a hose clamp.  The Liberty 331 transfer pump purred like a kitten, never even getting warm after an hour of semi-constant use.

I made one addition to the set-up, a 3 psi pressure gauge I plumbed to the bottom outlet of the tank.  Turns out a 3 psi gauge perfectly serves as a level indicator for a 2500 gallon tank.  The tank is essentially an 86" high water column, so 0 psi is empty, 3 psi is full.  (photo 2)

We're installing the 2500 gallon collection tank next.  We'll continue limping along on our bank of IBCs for a little longer.

And finally, the pad next to the house for the 2500 gallon collection tank.  We cloned the design from the first pad, as that half-full tank is behaving perfectly.

You can see one set of IBCs (our present collection tanks) in the background.  We're eager to get those out of there, but intend to keep them in place for roof collection this winter while we design the new gutter/downspout system for the 2500 gallon tank.  We as yet have no diverter, first flush, or overflow system (that's been me running around in the rain making near-continual adjustments), so the new design will be quite a bit more user-friendly.  For now, this "collection tank" will simply serve as additional storage.

But that's for future-us to figure out in the spring.  For now, we're off to the next project: sub-soiling, amending, and mulching the first 1/3 of our forest garden.  30 pick-up truck loads of 1/2-composted wood chips are ready to spread, with more chips arriving from the county roads crew weekly for the next 1/3 of the garden next fall.  Establishing healthy Forest Garden soil is what these tanks are all about.