How to Build a 550-gallon or larger IBC Tote Rainwater System for Off-Grid Use
In this example, we are going to use Two connected IBC totes, a pump, pressure tank, gauge, first-flush diverter and pressurized water outlets
For this project, we built a wooden platform to hold two 275-gallon IBC totes. Together, they will give us approximately 550 gallons of rainwater storage. Keep in mind that any decking to hold IBC totes needs to be as low to the ground as possible and be structurally capable of supporting over 5,000 lbs. For this reason, most people place the entire system on very compact ground. It also must be as level as absolutely possible or overtime the entire system can begin to lean and worst case scenario completely collapse under the weight of it all.
Our goal is not simply to collect water in two large containers. We are building a working water system that will automatically provide pressure when we open a faucet, supply water to the nearby structure, whether it is a barn, greenhouse or cabin, and operate a garden hose without having to turn the pump on and off manually.
The completed system will include:
Gutters and leaf protection along the building roof
A downspout and first-flush diverter
Two interconnected 275-gallon IBC totes
Screened inlets, vents and an overflow
An external water pump
A pressure switch
A diaphragm-style pressure tank
A pressure gauge
A pressure-relief valve
A sediment filter
One line leading to the building
One line leading to an outdoor hose connection
A roof and side protection to keep sunlight off the totes
Rainwater harvesting systems can reduce runoff, conserve treated water and provide a valuable reserve for landscape use. Their basic components normally include the roof, gutters, debris screening, storage tanks, a delivery system and, when gravity is insufficient, a pump.
First, understand what is pressurized and what is not
The two IBC totes are atmospheric storage tanks. They must never be sealed and pressurized.
Each tote needs a screened vent so air can enter as water is pumped out and escape as rainwater enters. The pump draws water from the totes and pressurizes only the plumbing located after the pump.
The pressure tank is a separate, purpose-built vessel designed to hold water under pressure. It stores a smaller amount of pressurized water so the pump does not have to start every time a faucet is opened briefly.
The overall plumbing arrangement
This is the basic path the water should follow:
Building ROOF
↓
Gutter and leaf guard
↓
Downspout screen
↓
First-flush diverter
↓
Screened inlet or divided fill line
↓
IBC Tote A ← bottom equalizing manifold → IBC Tote B
↓ ↓
Individual shutoff valves and removable unions
↓
Common 1½-inch or 2-inch suction manifold
↓
Coarse pump strainer
↓
Water pump
↓
Pressure-system manifold or tank tee
├── Pressure tank
├── Pressure switch
├── Pressure gauge
├── Pressure-relief valve
└── Drain valve
↓
Post-pump sediment filter
↓
Distribution tee
├── Cabin water line
└── Outdoor hose bibBoth totes also need screened vents and an overflow near the top. The overflow must be routed away from the building foundation, platform footings and septic drain field.
UGA Extension recommends that tank overflows be at least as large as the water inlet so the system can safely handle more rain than the tanks can store.
A note about the intended water use
For this project, the collected water should be considered nonpotable rainwater.
Roof runoff can contain bird droppings, microorganisms, pollen, dust, smoke particles and chemicals originating from roofing, gutters, pipes or storage materials. Water that looks clear is not necessarily safe to drink.
Use only IBC totes with a verified history. Ideally, they should be food-grade totes that previously contained food products. Never use a tote that previously held pesticides, petroleum products, industrial chemicals or another unknown material. The CDC specifically advises against using water-storage containers that previously held toxic chemicals.
Keep rainwater plumbing completely separate from any potable well or municipal water system. requirements may apply when rainwater is piped into a building.
Label the totes, hose connection and structure fixtures:
NONPOTABLE RAINWATER — DO NOT DRINK
Side Note: Potable Water
If you plan to use any portion of this system for drinking, cooking, brushing teeth or other potable purposes, include a separate water line with its own shutoff valve when assembling the main plumbing. That branch must pass through a properly designed treatment and disinfection system selected according to water-testing results and local requirements. Ordinary sediment or carbon filtration alone should not be assumed to make collected rainwater safe to drink. The complete potable-water system is covered in a separate article so its filtration, disinfection, testing, cross-connection protection and maintenance requirements can be explained thoroughly and safely.
Step 1: Protect the water before it enters the totes
The cleaner the water is before it reaches the tanks, the easier the entire system will be to maintain.
Our roof collection system includes three levels of protection:
Leaf guards on the gutter to stop large leaves and branches.
A downspout screen to catch smaller debris.
A first-flush diverter to discard the first and dirtiest water coming off the roof.
The first water from a storm carries much of the dust, pollen, bird waste and other material that accumulated during the preceding dry period. The proper first-flush volume depends on the size of the roof feeding the system.
The inlet entering each tote should be screened against mosquitoes but remain accessible for cleaning.
Step 2: Decide how rainwater will enter both totes
There are two workable arrangements.
Parallel filling
The preferred arrangement is to divide the cleaned downspout flow so that water enters both totes at approximately the same rate.
A PVC sanitary tee or Y-fitting can divide the downspout into two branches, with one branch entering each tote through a screened top inlet.
Both tanks should then have:
A screened inlet
A screened vent
An overflow set at the same elevation
Parallel filling reduces the amount of water that must move through the bottom connecting pipe during a heavy storm.
Filling one tote first
The other arrangement is to send the downspout into Tote A and connect Tote A to Tote B with a large pipe near the top. Water fills the first tote, passes through the upper transfer pipe and then fills the second.
In this arrangement:
The upper transfer pipe should be large enough to carry storm inflow.
Tote B receives the final overflow.
Both totes still need screened vents.
The bottom manifold connects the tanks for equal withdrawal.
Do not rely on a small bottom hose alone to transfer all the incoming water during an intense rain. The first tote could fill and overflow faster than water can move through an undersized connection.
Step 3: Connect the two bottom outlets
Set both totes at exactly the same elevation. When their bottom outlets are connected, gravity will cause the water levels to equalize.
IBC outlet threads vary, so identify the exact valve thread before buying adapters. Many appear to be “two inch” but use different buttress, cam-lock or pipe-thread patterns.
At each tote, install the components in this order:
IBC outlet
↓
Correct IBC thread adapter
↓
Full-port shutoff valve
↓
Union or cam-lock connection
↓
Common manifoldGive each tote its own shutoff valve. This allows one tank to be isolated and removed without draining the other.
Use unions or cam-lock fittings so the plumbing can be disconnected for cleaning or repairs. Do not permanently glue the entire system directly to the tote valves.
A 1½-inch or 2-inch common manifold is usually better than a garden-hose-sized connection. Larger pipe allows the tanks to equalize more quickly and reduces suction restriction at the pump.
Ideally, bring both tote outlets into a central tee and take the pump supply from the center:
Tote A valve ─────┐
├── Center tee ── Pump supply
Tote B valve ─────┘Add a drain or flush valve at the lowest point of the manifold. Sediment will eventually collect there.
Support the manifold independently. Do not make the tote valves carry the weight of several feet of PVC pipe.
Step 4: Build the pump suction side correctly
The section between the tanks and pump is called the suction side. Even a tiny air leak here can prevent a pump from priming, although no water may visibly leak out.
Place the pump:
As close to the totes as practical
Preferably below the normal tote water level
On a firm, vibration-resistant base
Under weather protection
Where it can be reached for priming and service
Keeping the pump below the tote outlets creates a flooded suction, meaning gravity helps keep the pump filled with water.
Use pipe at least as large as the pump’s suction inlet. If the pump has a 1¼-inch inlet, do not reduce the suction line to ¾ inch.
A good suction arrangement is:
Common tote manifold
↓
Isolation valve
↓
Union
↓
Large, cleanable coarse strainer
↓
Short reinforced suction hose or rigid pipe
↓
Pump inletA short section of reinforced, vacuum-rated suction hose can prevent pump vibration from being transferred to the rigid tote plumbing. Ordinary garden hose is not appropriate because it may collapse under suction.
Avoid:
High spots that trap air
Long runs of undersized pipe
Numerous elbows
Fine cartridge filters before the pump
Loose threaded fittings
A coarse pump strainer can protect the pump, but fine filtration belongs after the pump. A clogged fine filter on the suction side can starve the pump and cause cavitation.
Install a check valve or foot valve only where the pump manufacturer specifies. Many self-priming jet pumps still require an initial manual priming and a correctly positioned check or foot valve to retain prime.
Step 5: Add dry-run protection
A pressure switch does not necessarily protect a pump when the totes run empty. When there is no water, pressure remains low and the switch may tell the pump to continue running.
Install one of the following:
A low-water float switch in one tote
An electronic dry-run pump protector
A pump controller with low-water shutdown
A low-pressure-cutoff pressure switch designed for the pump
Because the tote levels are connected, one float switch may monitor both tanks as long as both tote valves remain open.
Position the shutoff level above the pump intake so the pump stops before it begins drawing air. The switch or controller must be rated for the pump’s voltage and amperage. Otherwise, it should operate an appropriately rated relay or contactor.
Step 6: Connect the pump to the pressure tank assembly
The pump’s discharge line feeds a pressure manifold, commonly assembled around a brass or stainless-steel tank tee.
A tank tee normally provides connection points for:
The pump discharge
The pressure tank
The outgoing water line
The pressure switch
The pressure gauge
The pressure-relief valve
A drain valve
These are standard components of pressurized pump systems. Pentair, for example, packages a tank tee with a 30/50 pressure switch, 0–100 PSI gauge and 75 PSI relief valve in one of its pump installation kits.
The general arrangement is:
Pump discharge
↓
Union
↓
Pressure manifold or tank tee
├── Pressure tank
├── Pressure switch
├── Pressure gauge
├── Pressure-relief valve
└── Drain
↓
Filtered distribution lineThe pressure tank does not have to be positioned directly “in line.” It normally branches from the tank tee and shares the same pressure as the outgoing plumbing.
Install only one controlling pressure switch. Some jet pumps already have the pressure switch mounted on the pump.
Step 7: Set the pressure-tank precharge
A common pressure-switch setting is 30/50 PSI:
The pump turns on when pressure falls to approximately 30 PSI.
The pump turns off when pressure reaches approximately 50 PSI.
Before introducing water into the pressure tank:
Disconnect electrical power.
Drain the water system completely.
Confirm the water-pressure gauge reads zero.
Measure the air pressure at the tank’s air valve.
Set the precharge two PSI below the switch’s cut-in setting.
For a 30/50 switch, set the tank to 28 PSI.
For a 40/60 switch, set it to 38 PSI.
Pressure-tank manufacturer Amtrol specifies setting the precharge two PSI below the pressure-switch cut-in, with the system empty of water.
Do not increase the pressure-switch setting unless the pump can reliably reach the new cut-out pressure and every pipe, filter, tank and fitting is rated for it. A pump that cannot reach cut-out pressure will run continuously.
Step 8: Install the gauge and pressure-relief valve
The pressure gauge should be located near the pressure switch and tank so all three experience approximately the same system pressure.
The gauge allows you to see:
When the pump starts
When the pump stops
Whether pressure is falling while no water is being used
Whether the pump is struggling to reach cut-out pressure
Whether filters are becoming restricted
The pressure-relief valve protects the system if the pressure switch fails or the pump does not shut off. Use the relief setting specified for the pump system and pressure tank. Route any discharge where escaping water cannot injure anyone or damage electrical equipment.
Never plug or cap a relief-valve opening.
Step 9: Filter the water after the pump
Install a cleanable sediment filter on the pressure side after the tank tee.
For general hose and cleaning water, a washable sediment filter may be adequate. For drip irrigation, install the mesh filtration and pressure regulator required by the drip equipment. UGA Extension identifies filtration, a pressure reducer and a pressure gauge as important components of a home drip-irrigation system.
Do not automatically add a carbon filter unless there is a particular reason for it. Carbon filters can improve odor and taste, but they do not automatically make rainwater microbiologically safe.
Step 10: Divide the pressurized water into two branches
After the post-pump filter, install a tee to create two independently controlled lines.
Filtered pressure line
├── Shutoff valve → Cabin line
└── Shutoff valve → Outdoor hose bibGive each branch its own full-port shutoff valve and union.
Install a hose-bib vacuum breaker on the outdoor faucet, especially when hoses may be left lying in buckets, ponds, animal troughs or chemical sprayers.
For the cabin line:
Keep it separate from potable plumbing.
Clearly label all outlets.
Use pressure-rated plumbing materials.
Install a drain at a low point for winterization.
Check local plumbing requirements before supplying indoor fixtures.
Step 11: Add vents, overflow and sunlight protection
Every tote must be able to breathe. Cover vent openings with corrosion-resistant mosquito mesh.
The overflow should:
Be located near the top of the tank
Be at least as large as the incoming water line
Include mosquito screening
Carry water away from the cabin and platform
Empty into a rain garden, swale or stable drainage area
Building a roof over the totes is excellent. However, a roof alone may not block morning and evening sunlight. I would also cover or wrap the translucent sides while leaving valves and inspection points accessible.
Shade and opaque protection help reduce water temperature and algae growth.
Step 12: Protect the electrical equipment
Water and electricity require special care.
The pump should have:
A properly sized electrical circuit
Grounding
Code-compliant GFCI protection
A weatherproof disconnect or switch
Outdoor-rated wiring and enclosures
Protection from rain, flooding and condensation
Adequate ventilation around the motor
UGA Extension specifically recommends ground-fault protection for rainwater-harvesting pumps.
Have a qualified electrician make or inspect the final electrical connection, particularly if the pressure switch must be wired separately.
How to test the system without filling everything at once
Do not begin the first test with 550 gallons.
Initial leak test
Close the individual tote valves and add a small amount of water to each tote. Inspect the factory tote valves and adapters.
Then:
Open both tote valves.
Add approximately 6 to 12 inches of water.
Confirm that the levels equalize.
Inspect every manifold joint.
Leave the water standing long enough to reveal slow leaks.
Pressure-system test
Before turning on the pump:
Confirm the pressure-tank precharge.
Open both tote valves.
Confirm the pump has water available.
Prime the pump according to its manual.
Slightly open the outdoor faucet to allow trapped air to escape.
Energize the pump.
Watch the pressure gauge closely.
With a 30/50 switch, the pump should stop at approximately 50 PSI. Open the faucet and observe whether it restarts near 30 PSI.
Then close every outlet. The gauge should remain steady. If pressure falls while no water is being used, inspect for a plumbing leak or a leaking check valve.
Test each branch separately
Run the outdoor hose first and check:
Pressure
Flow
Pump cycling
Filter leaks
Movement or vibration in the suction plumbing
Then close the hose branch and test the cabin branch.
Manually activate the low-water float or pump-protection device to verify that it interrupts the pump without actually allowing the pump to run dry.
Common problems during startup
The pump will not prime
Likely causes include a closed tote valve, air leak in the suction line, improperly installed check valve, empty pump housing, clogged strainer or a high spot trapping air.
The pump runs but never reaches shutoff pressure
The pump may be undersized, the cut-out setting may be too high, there may be a major leak, or the pump may be drawing air. Confirm that the pump curve shows it can deliver water at the required pressure.
The pump starts and stops every few seconds
This is called rapid cycling. Common causes include incorrect pressure-tank precharge, an undersized or damaged pressure tank, a blocked pressure-switch connection or a leak.
One tote empties faster than the other
Confirm that both totes are level, both outlet valves are fully open, both vents are clear and the equalizing manifold is large enough.
Pressure falls when everything is closed
Check for leaking fixtures, loose fittings, a faulty check valve or water flowing backward through the pump.
The pump becomes noisy
A noisy or gravel-like sound can indicate restricted suction or cavitation. Clean the strainer, open all valves fully, remove unnecessary elbows and make sure the suction pipe is large enough.
Ongoing maintenance
Inspect the system at least monthly and before and after major storms.
Clean:
Gutter guards
Downspout screens
First-flush diverter
Tote inlet screens
Mosquito screens
Pump strainer
Post-pump sediment filter
Periodically inspect the bottom of the totes for sediment and flush the low-point drain. UGA Extension recommends regular inspection and cleaning because no screening system removes all debris.
Before freezing weather:
Disconnect power.
Drain the pump and filter housings.
Drain exposed pipes.
Open low-point drains.
Follow the pump and pressure-tank winterizing instructions.
How much water can the roof collect?
A practical estimating formula is:
Roof area in square feet × rainfall in inches × 0.623 × collection efficiency = gallons collected
Collection efficiency is commonly estimated at approximately 75 to 90 percent because some water is lost through splashing, first flush, evaporation and gutter overflow.
Once you know the square footage of the portion of your building roof feeding these totes, you can calculate approximately how much rain will fill the 550-gallon system.
