2026 RPS EngineeringWhy a Fiberglass Dome?
Anaerobic digesters and covered process tanks produce hydrogen sulfide and other corrosive gases that shorten the life of coated steel covers. FRP handles that environment without coatings: the resin system is rated for continuous H2S exposure from -30°F to 140°F, protected by a UV-stabilized gel coat. Each panel segment is cast in one piece on the mold, with no bolting or bonding inside a panel, and an integrally molded drip lip keeps condensate off the outside of the tank wall.
Not sure whether your application calls for fiberglass or aluminum? See the guide: Aluminum vs. Fiberglass: How to Choose — it compares materials, BABA compliance, H₂S resistance, and cost.
Design & Construction
Every RPS dome is designed to ASCE 7-22 and IBC 2021 loads for your project location, with a 3:1 safety factor on allowable stress. Design calculations are certified by a professional engineer licensed in the state of installation. The laminate starts with a C-veil corrosion barrier on the interior surface, builds structural thickness with chopped strand and woven roving, and finishes with an exterior-grade UV-protected gel coat in a color the owner selects.
Panels bolt together weather-tight on 3-foot centers with Type 316 stainless hardware, carried on FRP compression and tension rings with neoprene sponge gaskets at the radial joints. The design keeps horizontal thrust off the tank wall. Lifting lugs are embedded at the balance point of each segment, so panels can be handled during installation and removed later if the tank needs work.
Options & Accessories
Domes can be configured with personnel hatches (30″ × 24″, Type 316 stainless hinges and latches), adjustable aluminum air intake louvers with bird/bug screens, fiberglass dormer entries with full personnel doors (including heat-traced, explosion-proof frames where required), and skylight areas molded translucent for natural light over the tank. Accessory openings are molded and glassed from both the interior and exterior of the panel for full strength.
Available Sizes
Current mold sizes: 18 ft, 20 ft, 22 ft, 24 ft, and 30 ft diameter. Tell us your tank diameter and application and we’ll confirm fit, accessories, and access options for your installation.
Specification
The complete CSI-format spec section for FRP domes is available for project documents:
View Spec – FRP Dome – Section 43 42 34 Download PDF
Installed Projects
Get a Quote
Covering a digester or process tank? Send your tank diameter and application and we’ll recommend the right dome and accessories — with a complete submittal package for your engineer’s review. RPS is a WBENC-Certified Women’s Business Enterprise (#WBE2601717); purchases can count toward WBE participation goals.
gina-wwtp@rpsengineering.com · 847-931-1950
Frequently Asked Questions
What sizes of fiberglass dome covers are available?
Current mold sizes are 18, 20, 22, 24, and 30 ft diameter. Send your tank dimensions and we’ll confirm which dome fits your installation and what accessories are available at that size.
Why choose a fiberglass dome over aluminum for a digester?
The atmosphere above an anaerobic digester is one of the most corrosive in a treatment plant. FRP resin systems are rated for continuous hydrogen sulfide exposure and need no coating maintenance, which is why fiberglass is the usual choice for digesters and other high-H2S applications. In less aggressive atmospheres aluminum can make sense; our material guide walks through the decision.
How are the domes constructed?
Each panel segment is cast in one piece on the mold with a corrosion-barrier laminate interior, structural layers of woven roving and chopped strand, and a UV-protected gel coat exterior. Panels interlock weather-tight with Type 316 stainless bolts on 3-foot centers, supported by FRP compression and tension rings, with a 3:1 design safety factor on all load combinations.
What access and ventilation options are available?
Personnel hatches, adjustable aluminum air intake louvers with bird/bug screens, fiberglass dormer entries with full personnel doors, and translucent skylight areas. Openings are molded and reinforced from both sides of the panel — locations are set on your drawings.
What design loads are the domes engineered for?
Dead, snow, and wind loads per ASCE 7-22 and IBC 2021 for your project location, with calculations certified by a professional engineer licensed in the state where the dome is installed. Design accommodates thermal expansion from -20°F to 100°F ambient, and horizontal thrust is not transmitted to the tank wall.
How do I get pricing, and what’s the lead time?
Budget pricing is available from tank diameter and application. Firm quotes follow drawings and field-verified dimensions, since each dome is engineered to the specific tank. Contact the RPS Design Team at gina-wwtp@rpsengineering.com to scope timing for your project.
