Snyder Industries 4000 Gallon HDLPE Vertical Double Wall Liquid Chemical Storage Tank (1.9 SG)

A spill plan in one footprint

Regulated chemical in a single wall tank needs a berm that holds the whole tank, and at 4,000 gallons that is a concrete basin, a sump, a drain valve that must stay closed, and a rain problem. A double wall tank keeps its containment inside the outer shell, so the 102 inch footprint is all the room it needs and the tank can stand inside an occupied building where a spill must never reach a floor drain; the SPCC 40 CFR 112 compliance walkthrough explains which spill-plan cases a double wall tank satisfies by itself. The rated chemistry for the resin is listed below; check the liquid at its concentration in the chemical compatibility database, because weight rating and chemical resistance are separate properties, and work out the usable volume once thermal expansion and the interstice are accounted for with the Captor double wall freeboard sizing guide. The tank sizing calculator matches the volume to feed rate and delivery interval, and the tank sizing guide covers the reserve.

Grades on the 102 x 178 inch double wall, and the sizes beside it

The N43 is the 1.5 specific gravity grade, 800 pounds lighter, for coagulants and brines that never approach the density this wall is sized for, and the N40 is cross-linked polyethylene for oxidizers at that same weight. The N30 is the sulfuric acid grade at this tank's weight. The 5600000N30 is the 3,500 gallon double wall, 20 inches shorter on the same base, and the 5620000N30 is the 4,500 gallon step up at 197 inches.

Settled on the 4000 gallon tank? Freight to your ZIP and add to cart above; a written quote is one click away for the paperwork.

Openings, with the alarms that go on them

• Access: 18 inch threaded, vented manway on the primary, 178 inches up; dip-tube fill; vent line to the outside on caustic and acid, sized for a tanker's unload rate.
• Outlet: through both walls as one penetration, flanged, with an expansion joint and the valve carried off the slab; order the fitting in the material the chemical calls for.
• Service limit: 120 F / 48 C.

Two levels to watch: the primary, with a sender chosen for the chemical per the level gauge selection guide, and the space between the walls, which serves as the leak alarm and gets a switch, a shift check at the port, and a weekly log entry. A wet interstice is a failed primary, and the tank is drained the same day. The tanker connection is where an overfill starts; the tank spillover redundancy guide walks through the alarm and cutoff layers that stop an overfill upstream of the interstice. Keep the outer shell clear: nothing leaned on it, nothing bolted through it, nothing stored in the space.

The slab and the platform

Full, the tank loads a 102 inch circle to 63,384 pounds at the rating, and a rotationally molded floor bears on the whole pad, so the pad is what matters: an engineered slab in full contact under the entire floor, screeded flat, with no pipe trench or drain crossing under it. Straps go on while the tank is empty, because 178 inches of empty polyethylene is a sail, and the straps go slack once the tank is full and its own weight anchors it. The manway is reached from a fixed platform on its own footings, not hung from the tank, with a rail, and the interstitial port is where the operator can see it from the ground.

The first delivery

The driver's pump can deliver faster than the manway vent can breathe, so the vent is sized for the unload rate or the fill goes through a dedicated top bulkhead with its own vent line. The fill pipe reaches the floor, so caustic or coagulant enters below the surface instead of free-falling and foaming. If the tank is ever used to dilute a batch, water goes in first and the chemical second; the other order boils. Watch the first delivery from the first gallon to the last, with eyes on the slab edge, the outlet fitting and the interstitial port as the tank fills, and the log takes the date and strength of every load that follows.

Inspecting the primary

A polyethylene wall fails first in the headspace, where vapor and ultraviolet work on it, not at the liquid line, so the annual inspection is done from the platform with the manway open and a light, looking for crazing and chalking in the top third of the primary. The interstitial port is the daily check, and a dry port is the whole point of the second wall. The outlet penetration and the flanged transition are checked at every delivery, because that is where a tank this heavy moves as the level changes, and the expansion joint is what takes that movement instead of the fitting.

Jobs it is bought for

Caustic, coagulant and acid bulk storage at water systems that cannot build a berm, chemical storage inside occupied buildings, and any regulated liquid at plant scale at a site an inspector visits. One chemical to a tank, a label both inspectors can read, and the manway kept closed against vapor loss.

Chemical service ratings

The resin is rated for the liquids below at the concentrations shown; the fitting and gasket called out are the ones to order with the tank. Verify the exact service on the linked page or in the chemical compatibility database before ordering.

• Acetic Acid 60% with PP/PVC fittings and EPDM gaskets
• Aluminum Sulfate 50% with PVC fittings and EPDM gaskets
• Calcium Chloride 40% with PVC fittings and EPDM gaskets
• DEF 32.5% with 316SS fittings and EPDM gaskets
• Ethylene Glycol 100% with PVC fittings and EPDM gaskets
• Ferric Chloride 50% with PVC fittings and EPDM gaskets
• Ferric Sulfate 60% with PVC fittings and EPDM gaskets
• Ferrous Sulfate 20% with PVC fittings and EPDM gaskets
• Hydrochloric Acid 37% with PVC fittings and Viton gaskets
• Hydrofluoric Acid 48% with PP/PVC fittings and Viton gaskets
• Hydrofluosilicic Acid 26% with PP/PVC fittings and Viton gaskets
• Hydrogen Peroxide 50% with PVC fittings and Viton gaskets
• Magnesium Chloride 30% with PVC fittings and EPDM gaskets
• Peracetic Acid 30% with 316SS fittings and Aflas gaskets
• Phosphoric Acid 85% with PVC fittings and Viton gaskets
• Polyaluminum Chloride with PVC fittings and EPDM gaskets (confirm rated concentration against the chart)
• Potassium Carbonate 50% with PVC fittings and EPDM gaskets
• Potassium Hydroxide saturated with PVC fittings and EPDM gaskets
• Propylene Glycol with PP/316SS fittings and EPDM gaskets (confirm rated concentration against the chart)
• Sodium Bisulfate with PVC/PP fittings and EPDM gaskets (confirm rated concentration against the chart)
• Sodium Bisulfite with PVC/PP fittings and EPDM gaskets (confirm rated concentration against the chart)
• Sodium Carbonate 30% with PVC fittings and EPDM gaskets
• Sodium Hypochlorite at less than 16.5% with PVC fittings and Viton gaskets
• Sodium Thiosulfate 40% with PVC fittings and EPDM gaskets
• Sulfuric Acid 98% with CPVC fittings and Viton gaskets
• Urea Solution 50% with PP/PVC fittings and EPDM gaskets
• Zinc Orthophosphate with PP/316SS fittings and EPDM gaskets (confirm rated concentration against the chart)

What the carrier needs from you

At 102 inches across and 178 inches long on the deck the 5610000N45 is oversize freight (NMFC 156600) on a flatbed at a lane rate; the freight cost estimator gives the flatbed number for your ZIP, and the listed price is before freight. A crane or a forklift with long forks sets 3,200 pounds on the slab. Water-test the primary and hold it long enough to prove the interstice stays dry, then drain and dry the tank before the first delivery. Note the pad height and the outlet height on the site plan while the tape is out; the next pipe run will need both.