Top 10 Tanks & Covers Manufacturers for Water and Wastewater

Introduction

Liquid storage and containment are fundamental to the integrity of any treatment plant or distribution network, yet they are often treated as static commodities rather than dynamic process vessels. For municipal consulting engineers and utility directors, the failure of a storage tank represents more than just a leak; it signifies a catastrophic breach of sanitary barriers, a fire protection liability, or a significant environmental violation. While pumps and sensors often garner the majority of the instrumentation and control (I&C) budget, the capital expenditure (CAPEX) for storage infrastructure is massive, and the long-term operational expenditure (OPEX) regarding coating maintenance can cripple a utility’s budget if the initial specification is flawed.

When evaluating the Top 10 Tanks & Covers Manufacturers for Water and Wastewater, engineers must navigate a complex landscape of material science—balancing the benefits of prestressed concrete, glass-fused-to-steel, welded steel, and fiberglass reinforced plastic (FRP). The selection process is rarely about finding a single “best” brand, but rather matching the specific chemistry, geotechnical conditions, and lifecycle requirements of a project with a manufacturer’s core competency. A bolted steel tank perfect for a rural potable water standpipe may be wholly unsuited for an acidic anaerobic digestion process.

This article provides a technical framework for navigating the marketplace of the Top 10 Tanks & Covers Manufacturers for Water and Wastewater. It moves beyond glossy brochure claims to focus on engineering fundamentals: corrosion resistance mechanisms, structural integrity under seismic loading, adherence to AWWA standards, and constructability in restricted footprints. The goal is to equip design engineers and plant managers with the criteria necessary to write defensible specifications and select equipment that ensures decades of reliability.

How to Select / Specify

Selecting storage solutions requires a multi-dimensional analysis that accounts for process chemistry, structural loads, and long-term maintenance strategies. When reviewing potential vendors among the Top 10 Tanks & Covers Manufacturers for Water and Wastewater, the following engineering criteria must be defined in the Basis of Design (BOD).

Duty Conditions & Operating Envelope

The “fluid” is rarely just water. In wastewater applications, the headspace gas composition is as critical as the liquid.

• Ph Range & Chemical Attack: For industrial wastewater or anaerobic digestion, pH swings can aggressively attack standard epoxy coatings. Glass-fused-to-steel (GFS) or Type V concrete mixes may be required.
• Temperature Gradients: Biological processes like thermophilic digestion operate at elevated temperatures (50-60°C). The tank material and its expansion coefficients must accommodate thermal cycling without compromising seal integrity.
• Operating Pressure: While most storage is atmospheric, digesters often operate at slight positive pressures. The tank and cover interface must be designed to contain gas without leakage, requiring gas-tight specifications rather than simple weather protection.
• Turnover Rates: High-cycling tanks (like wet weather equalization basins) experience different fatigue stresses than static fire water storage.

Materials & Compatibility

Material selection is the primary driver of lifecycle cost.

• Prestressed Concrete (AWWA D110): Offers the highest durability and lowest maintenance but requires significant upfront CAPEX and heavy civil site work. It is inherently corrosion-resistant without coatings.
• Bolted Steel (AWWA D103): Available in various coatings. GFS is the premium option for wastewater; epoxy-coated bolted steel is a cost-effective solution for potable water but relies heavily on the quality of the field application or factory cure.
• Welded Steel (AWWA D100): The traditional choice for very large volumes (multi-million gallon). It allows for custom geometries but requires rigorous field coating inspection and regular recoating intervals (15-20 years).
• Aluminum Covers: For covers, aluminum is the standard for corrosion resistance in H2S-rich environments, preventing the “concrete rot” often seen on the underside of older concrete dome covers.

Hydraulics & Process Performance

The tank is a process reactor.

• Mixing Characteristics: In wastewater treatment, solids suspension is critical. The tank geometry (aspect ratio) must support the selected mixing technology (jet, mechanical, or gas mixing) to prevent “dead zones” where solids accumulate and go septic.
• Baffling: For chlorine contact basins, short-circuiting is a failure mode. The internal structure must accommodate baffle walls to ensure required detention times (CT values).
• Vortex Prevention: Outlet design must prevent vortex formation during drawdown, which can entrain air and damage downstream pumps.

Installation Environment & Constructability

How the tank gets built is often as important as how it performs.

• Restricted Access: In retrofits, heavy cranes may not be able to access the site. Bolted steel tanks, which can be jacked up from grade, or panelized tanks offer significant advantages over cast-in-place concrete or large welded sections.
• Geotechnical Constraints: High differential settlement risks may favor steel tanks (which have some ductility) over concrete, or require deep pile foundations that skew the cost analysis.
• Seismic Zones: High seismic zones require specific anchoring details and freeboard calculations to account for sloshing waves (convective forces).

Reliability, Redundancy & Failure Modes

Engineers must plan for the “unhappy path.”

• Coating Failure: The most common failure mode for steel tanks. A holiday (pinhole) in the coating leads to concentrated corrosion. Cathodic protection (sacrificial anode or impressed current) is a mandatory redundancy for steel assets.
• Seal Failure: In bolted tanks, the gasket or mastic material is the weak link. Specifications should require EPDM or specific synthetic rubbers compatible with the stored fluid.
• Structural Fatigue: Floating covers on reservoirs are subject to wind flutter and UV degradation. Failure leads to sinking, which is a massive retrieval and repair operation.

Maintainability, Safety & Access

Operational reality often clashes with “low bid” design.

• Accessways: AWWA standards set minimums, but operational best practice dictates larger manways (30-inch minimum) for personnel access with SCBA gear, especially in wastewater applications.
• Washdown: Sloped floors with center sumps significantly reduce the labor hours required for tank cleaning compared to flat floors.
• Safety: Exterior ladders vs. spiral stairs. Spiral stairs are preferred for operators carrying tools or sampling equipment. Fall protection and davit arm bases for retrieval winches must be integrated into the tank manufacturing.

Lifecycle Cost Drivers

A Total Cost of Ownership (TCO) calculation usually reveals that the “cheapest” tank (often field-welded with standard epoxy) is the most expensive over 40 years due to recoating requirements.

• CAPEX: Concrete > GFS > Welded Steel > Bolted Epoxy (Typical hierarchy, varies by size).
• OPEX: Steel tanks require full interior sandblast and recoat every 15-25 years. Concrete tanks essentially require zero structural maintenance, only cleaning.
• Downtime Costs: Taking a clearwell or digester offline for 6 weeks for recoating requires bypass pumping and temporary storage, costs often ignored in initial bids.

Comparison Tables

The following tables provide an engineer-to-engineer comparison of the leading manufacturers and technology types. Table 1 focuses on the Top 10 Tanks & Covers Manufacturers for Water and Wastewater based on market presence, installed base, and technological capability. Table 2 analyzes the application fit for different tank technologies.

Table 1: Top 10 Tanks & Covers Manufacturers (Alphabetical) – Engineering Profile

Manufacturer	Primary Technology/Strength	Best-Fit Applications	Limitations / Considerations	Maintenance Profile
CST Industries (Aquastore)	Glass-Fused-to-Steel (Bolted)	Potable water, wastewater digesters, aggressive leachate.	Higher CAPEX than epoxy steel. Panel replacement difficult if damaged structurally.	Extremely Low. Glass coating does not require recoating. Gasket maintenance only.
DN Tanks	Prestressed Concrete (AWWA D110)	Large volume potable storage, equalization basins, buried tanks.	High initial CAPEX. Heavy civil construction footprint. Difficult to modify later.	Near Zero. No coating to fail. 50-100 year design life.
McDermott (CB&I)	Welded Steel / Elevated Storage	Massive scale water storage, iconic elevated towers (Waterspheroid).	Requires rigorous field welding and field coating inspection. Long construction time.	Moderate/High. Requires full interior/exterior recoating every 15-25 years.
Superior Tank Co.	Bolted & Welded Steel	Fire protection, potable water, oil & gas.	Heavily dependent on coating selection (Epoxy vs. Powder). Size limitations on bolted models.	Moderate. Gasket inspections and eventual recoating required.
Caldwell Tanks	Multi-Type (Composite, Steel, Concrete)	Elevated water storage, custom municipal tanks.	Large site laydown area required. Project management intensive due to scale.	Varies by type. Composite (concrete shaft) reduces maintenance vs. all-steel towers.
Landmark Structures	Composite Elevated Tanks (CET)	High-visibility municipal elevated storage.	Niche focus on elevated storage. High engineering cost for custom designs.	Low/Moderate. Concrete shaft requires little care; steel bowl requires coating maintenance.
Geomembrane Technologies (Evoqua/Xylem)	Flexible Covers & Odor Control	Wastewater basins, clarifier covers, odor containment.	Not a tank manufacturer (covers only). Soft covers susceptible to tears/UV over long term.	Moderate. Tensioning adjustments and fabric inspection required.
Ultraflote	Aluminum Geodesic Domes / Floating Covers	Covering open reservoirs, retrofitting existing open-top tanks.	Specialized in covers. Aluminum is robust but vulnerable to caustic splash in high pH.	Low. Aluminum is self-protecting. Check gaskets and structural nodes.
Containment Solutions (NOV)	Fiberglass (FRP)	Underground storage, corrosive chemical storage, OSI.	Capacity limits (rarely exceeds 50k-60k gallons). Brittle failure mode if impacted.	Low. No corrosion. Inspect for UV degradation (fiber bloom) on aboveground units.
Columbian TecTank (part of CST)	Epoxy Coated Bolted Steel	Dry bulk, potable water, industrial process water.	Epoxy coating is less durable than glass in aggressive wastewater.	Moderate. Requires cathodic protection and periodic coating rehab.

Table 2: Tank Technology Application Fit Matrix

Application Scenario	Preferred Technology	Why? (Engineering Rationale)	Key Constraint
Anaerobic Digester	Glass-Fused-to-Steel or Prestressed Concrete	Resistance to H2S corrosion and acidic headspace is mandatory. Gas tightness is critical.	Temperature expansion differentials.
2.0 MG Potable Water (Ground)	Prestressed Concrete	At this volume, concrete becomes cost-competitive and offers lowest 50-year TCO.	Site access for heavy equipment.
0.2 MG Fire Water (Remote)	Bolted Steel (Epoxy)	Ease of transport to remote sites; quick assembly (jacking system). Lowest CAPEX.	Must install Cathodic Protection.
Clarifier Cover (Odor Control)	Aluminum Geodesic Dome	Clear span capability eliminates internal columns; aluminum resists humidity/H2S.	Snow load ratings.
Aggressive Ind. Effluent	FRP or Glass-Fused-to-Steel	Standard epoxy and concrete will be eaten by extreme pH shifts.	Chemical compatibility of gaskets.

Engineer & Operator Field Notes

Experience in the field often highlights the gap between a manufacturer’s specification and the operational reality. The following notes cover critical aspects of executing projects involving the Top 10 Tanks & Covers Manufacturers for Water and Wastewater.

Commissioning & Acceptance Testing

Acceptance testing is the only leverage an engineer has to ensure quality before final payment.

• Holiday Testing (Spark Test): For coated steel tanks, 100% holiday testing is non-negotiable. This detects microscopic pinholes in the coating that will become rust blisters within months. This must be done after assembly, not just at the factory.
• Hydrostatic Testing: Fill the tank in stages (e.g., 25%, 50%, 75%, 100%) over several days to monitor foundation settlement. Differential settlement can crack concrete rings or warp steel shells.
• Gas Tightness (Digesters): For digester covers, positive pressure testing with soap solution on weld seams/bolt patterns is required to ensure no biogas leaks.
• Disinfection (Potable): Adherence to AWWA C652 for chlorination and bacteriological testing is mandatory before the tank can be brought online.

PRO TIP: Always specify a “hold point” for foundation inspection before the tank floor is laid. Once the steel or concrete floor is down, verifying subgrade compaction or the presence of a proper sand cushion is impossible.

Common Specification Mistakes

Errors in the Request for Proposal (RFP) often lead to change orders or premature failure.

• Ignoring Cathodic Protection: Specifying a steel tank without a passive or impressed current cathodic protection system is engineering malpractice in most soil/water conditions. It is the cheapest insurance for the tank’s life.
• Vague “Or Equal” Clauses: Comparing a bolted epoxy tank to a glass-fused tank is not an “equal” comparison regarding lifecycle. Specifications must clearly delineate allowed technologies or use a base-bid plus alternate structure.
• Undersized Vents: Screened vents must be sized not just for air displacement during filling, but for vacuum prevention during rapid drawdown (e.g., fire pump activation). Tank implosion due to vacuum is a real and catastrophic failure mode.

O&M Burden & Strategy

Operators must live with the design for decades.

• Washout Intervals: Potable tanks typically require inspection/cleanout every 3-5 years. Design the site layout to accommodate discharge of the full tank volume to a sanitary sewer or storm drain (with dechlorination).
• Anode Replacement: Sacrificial anodes in steel tanks are consumables. They should be checked annually and typically replaced every 5-10 years.
• Exterior Cleaning: For GFS tanks, the exterior cleans easily with rain. For concrete, pressure washing may be needed for aesthetics. For rough-coated steel, mildew growth can be problematic in humid climates.

Design Details / Calculations

Incorporating specific design logic helps differentiate a generic project from a properly engineered system.

Sizing Logic & Methodology

Sizing is rarely just “Average Daily Flow.”

1. Equalization Volumes: Calculate based on the diurnal flow curve. The tank must absorb the peak hour flow minus the treatment plant capacity.
2. Fire Flow: Check NFPA requirements. Fire storage is “dead volume” that sits at the bottom of the tank and cannot be used for operational buffering.
3. Freeboard: Add 12-24 inches minimum above the overflow weir level to the roof structure to prevent splashing against the vents/roof during seismic events or wave action.

Specification Checklist

When drafting specs for the Top 10 Tanks & Covers Manufacturers for Water and Wastewater, ensure these sections are populated:

• Design Standard: Explicitly state AWWA D100, D103, or D110.
• Wind & Seismic Load: Cite the specific ASCE 7 version and local code values (e.g., 150 mph wind, Seismic Site Class D).
• Foundation: Ring wall vs. slab-on-grade vs. granular ring. This interface is critical.
• Accessories: Level transducer mounting flanges, sample taps, exterior and interior ladders, safety cages, and confinement berms.

Standards & Compliance

• AWWA D100: Welded Carbon Steel Tanks for Water Storage.
• AWWA D102: Coating Steel Water-Storage Tanks.
• AWWA D103: Factory-Coated Bolted Carbon Steel Tanks for Water Storage.
• AWWA D110: Wire- and Strand-Wound, Circular, Prestressed Concrete Water Tanks.
• NSF/ANSI 61: Drinking Water System Components (Mandatory for all wetted materials in potable service).

FAQ Section

What is the primary difference between AWWA D103 and AWWA D100 tanks?

AWWA D103 refers to factory-coated bolted steel tanks, where panels are manufactured and coated in a controlled factory environment and assembled on-site with gaskets and bolts. AWWA D100 refers to welded steel tanks, which are assembled from steel plates and welded on-site, requiring field surface preparation (sandblasting) and coating. D103 tanks are generally faster to erect, while D100 tanks have fewer size limitations.

When should an aluminum geodesic dome be selected over a flat steel cover?

Aluminum geodesic domes are preferred for large diameters (over 40-50 feet) because they are self-supporting and do not require internal columns, which interfere with mixers or scrapers. They are also inherently corrosion-resistant, making them ideal for wastewater applications where H2S gas would rapidly corrode the underside of a flat steel or concrete roof. They are often lightweight, reducing the load on the tank walls.

What is the typical lifecycle of a Glass-Fused-to-Steel (GFS) tank?

A GFS tank is designed to provide a service life comparable to concrete, often exceeding 40-50 years, provided the sealants (gaskets/mastic) are maintained. The glass coating is chemically fused to the steel and does not degrade, chalk, or peel like epoxy paints. Unlike welded steel tanks that need recoating every 15-20 years, GFS tanks typically only require periodic resealing of joints.

Why are prestressed concrete tanks preferred for buried applications?

Prestressed concrete tanks (AWWA D110) are structurally superior for buried or partially buried applications because they can withstand significant external soil pressures that would buckle an empty steel tank. Concrete is also naturally resistant to soil corrosion, whereas buried steel requires aggressive external coating and cathodic protection to survive.

How does the cost of a stainless steel tank compare to a coated carbon steel tank?

Stainless steel tanks (bolted or welded) typically carry a CAPEX premium of 30-50% over coated carbon steel. However, for specific industrial wastewater applications or food-grade requirements where coating integrity is a risk, the elimination of recoating costs can result in a lower Total Cost of Ownership over 20 years. They are less common in large municipal storage due to the high material cost.

Do I need cathodic protection for a concrete tank?

Generally, no. The prestressing wires in an AWWA D110 tank are encased in shotcrete or grout, which provides a high-alkaline environment that passivates the steel and prevents corrosion. However, inspection of the exterior shotcrete for cracking is necessary to ensure moisture does not penetrate to the steel reinforcement.

How do you select the top 10 tanks & covers manufacturers for water and wastewater projects?

Selection should be based on the manufacturer’s adherence to relevant AWWA standards (D100/D103/D110), their Experience Modification Rate (EMR) for safety, the availability of local service crews, and their specific track record with the fluid being stored. Engineers should require a list of 5 installations of similar size and service age (>10 years) to verify long-term coating performance.

Conclusion

Key Takeaways

• Material Matches Application: Use Glass-Fused-to-Steel for aggressive wastewater/digesters; use Prestressed Concrete for massive, long-life potable storage; use Bolted Epoxy for cost-effective remote water storage.
• Standards are Mandatory: Never specify a tank without citing the specific AWWA standard (D100, D103, D110). This protects the utility from non-compliant agricultural-grade products.
• The Hidden Cost of Coatings: A cheaper welded steel tank may cost 2x its purchase price in recoating over 40 years. Factor this OPEX into the bid evaluation.
• Venting is Critical: Ensure vents are sized for maximum pump-out rates to prevent vacuum collapse—a rare but devastating failure mode.
• Cathodic Protection: Always include CP systems for steel tanks. It is a minor upfront cost that extends asset life significantly.

Selecting from the Top 10 Tanks & Covers Manufacturers for Water and Wastewater is not a simple procurement exercise; it is a major engineering decision that dictates the reliability of the plant for the next half-century. Whether the project demands the monolithic durability of DN Tanks’ concrete, the chemical resistance of CST’s Aquastore, or the massive scale of a McDermott welded tower, the successful engineer looks past the initial bid price.

By prioritizing the physics of corrosion protection, the reality of site constructability, and the inevitability of maintenance, engineers can specify storage solutions that remain invisible to the public—which, in the world of water infrastructure, is the ultimate mark of success.

source https://www.waterandwastewater.com/top-10-tanks-covers-manufacturers-for-water-and-wastewater/