The short version
- Bottom-link with 2-inch full-bore fittings, never 3/4-inch.
- One isolation valve per tank turns a maintenance shutdown into a twenty-minute job.
- Vent the array or the draw will collapse a bottle.
- Level the base before filling; linked tanks redistribute their own weight.
Why manifold rather than buy a tank
The customers who ask for this almost always have the same constraint: they need somewhere between 1,000 and 3,000 gallons of standing volume, and they cannot get a fixed tank into the building. A doorway, a low ceiling, a mezzanine, a landlord who will not permit civil works.
Four 275 gallon totes go through a 48-inch door one at a time and give you 1,100 gallons behaving as a single vessel. The whole array costs perhaps $1,100 in containers plus $600 to $900 in fabrication, against $9,500 installed for a comparable fixed tank — and you can take it apart and move it.
What you give up is simplicity. A fixed tank has one connection and one failure mode. An array has four containers, five or six joints, and a set of ways to get it wrong that I will now go through, because I have got most of them wrong at least once.
Bottom-link, full bore
The containers link at their outlets, in a row, with the draw taken from one end. Gravity equalises the levels, so the array behaves as one vessel with four times the capacity and one place to connect a pump.
Use 2-inch fittings. I have been called out to arrays linked with 3/4-inch garden hose fittings more times than I would like, and they do not work — the restriction means the tanks take hours to equalise, so in practice you have four separate tanks that happen to be joined. When you draw from the end one, it empties while the others slowly trickle across.
Camlocks on every joint, so a tank can be disconnected without cutting anything. And a short flexible section in each link, because rigid plumbing between four independently settling containers eventually cracks something.
An isolation valve per container
This is the single detail that separates an array somebody can live with from one they come to resent. Without isolation valves, cleaning one container, replacing one gasket or removing one damaged tank means draining 1,100 gallons.
With them, you close two valves, disconnect two camlocks, and lift the container out with a forklift. Twenty minutes, no lost product. The valves cost about $24 each. I fit them as standard now and I do not offer the option not to.
| Component | Per array of four | Why |
|---|---|---|
| 2 in butterfly isolation valves | 4 × $24 | Remove one tank without draining the array |
| 2 in camlock adapters and couplers | 8 × $18 | Disconnect without cutting |
| Flexible link sections | 3 × $22 | Absorb differential settlement |
| Common vent line and breather | 1 × $60 | Prevents vacuum collapse on draw |
| Sight tube at the draw end | 1 × $34 | Level for the whole array at a glance |
| Bunded steel frame | Quoted | Containment sized to one container plus freeboard |
Vent it, or you will collapse a bottle
Four sealed containers being drawn down through a pump is four containers pulling a vacuum. HDPE has essentially no resistance to negative pressure — the top panels come in, the dent is permanent, and the deformed area becomes a stress concentration that crazes early.
The fix is a common vent line joining the lids with a single breather at the high point. It also stops the array breathing moist outside air in and out of every lid individually, which matters if you care about what is in the headspace.
The cheap version
The base is structural, not cosmetic
Four full 275 gallon totes of water are 9,672 lb. Linked, they equalise — which means if the ground is not level, the low container ends up carrying disproportionate load while the high one sits half empty.
On a concrete pad this is a non-issue. On compacted gravel it is manageable if you level properly first. On soil it will go wrong within a wet season: the ground settles unevenly, a pallet twists, a base cracks at a corner, and you find out at three in the morning.
For anything holding a regulated liquid we build a bunded steel frame sized to the largest container plus freeboard, forkable, with a sump drain and a grate deck. It is not cheap, but the alternative is discovering what 275 gallons of your product does to a floor drain.
How big is too big
Two to eight containers works well. Beyond eight the linking losses start to matter, the frame gets expensive, and the honest answer is usually a fixed tank if the site permits one.
The other crossover is around 10,000 gallons of standing volume, or as soon as you are taking delivery by tanker rather than by pallet. At that point the handling economics that make totes attractive have inverted and you should be talking to a tank installer, not to me.
Written by Tomás Beltrán, fabrication lead at IBC Totes San Francisco. Published July 2, 2025. Spotted something wrong? Tell us — we would rather fix it than defend it.