Plastic chambers have won many small-diameter jobs, but on roads, highways and large storm systems, precast concrete is still the backbone of Georgian infrastructure. Concrete manhole rings, base units, cover slabs, open drainage trays (*лотки*) and box collectors are heavy and robust, and they are familiar to every contractor. This article explains where concrete wins, what to check, and how it combines with cast-iron covers and HDPE pipe.
Precast elements at a glance
| Element | What it is | Typical use |
|---|---|---|
| Manhole rings / sections | Circular units, DN 1000–2000 typical, stacked | Sewer and storm chambers |
| Base units (with benching) | Bottom section with formed channels | Faster than benching cast on site |
| Cover slabs / reducing slabs | Top slab with an opening for the frame | Carries the cast-iron cover and frame |
| Adjusting rings | Thin rings for final height | Fine-tunes the cover to road level |
| Open drainage trays (lotki) | U- or V-shaped channels | Roadside ditches, slopes, irrigation |
| Box / rectangular collectors | Large closed sections | Storm collectors, culverts, utility tunnels |
Reference standard for manholes and inspection chambers: EN 1917.
Concrete vs plastic chambers
| Criterion | Precast concrete | Plastic (PE/PP) chamber |
|---|---|---|
| Load capacity | Very high; suits deep and heavily trafficked locations | Depends on surround; usually lighter duty |
| Buoyancy in high groundwater | Heavy, so resists uplift | May need anchoring |
| Weight / handling | Crane required | Lifted by hand or a small excavator |
| Corrosion in sewers | Can be attacked by H₂S; needs a lining or resistant concrete | Fully resistant |
| Large diameters (DN 1500+) | Standard | Limited |
| Cost on big chambers | Economical | Rises steeply with size |
Rule of thumb: use concrete for large, deep or road chambers and storm collectors, and plastic for small inspection chambers in landscaped and private areas.
Quality checks on delivery
- Dimensions and wall thickness match the drawings.
- No cracks, honeycombing or exposed reinforcement.
- Joints have rubber seals or profiles for watertightness.
- Step irons or ladders fitted and corrosion-protected.
- Lifting anchors are suitable for the site crane.
Installation tips
- Lay the base on a compacted, level blinding concrete layer.
- Seal every joint, then backfill evenly around the chamber.
- Use adjusting rings so the cast-iron frame sits at final road level. A telescopic frame is an alternative for roads that will be resurfaced.
- Connect pipes with flexible joints close to the chamber wall to allow for settlement.
What to write in the BOQ
*"Precast concrete manhole DN 1500 to EN 1917, comprising base unit with benching, rings with rubber joint seals, reducing cover slab, adjusting rings and step irons; cast-iron cover and frame EN 124 D400 Ø600 clear opening; including blinding, bedding mortar and backfill."*
Quick selector
- Road storm chamber, 3 m deep → concrete rings + base + D400 cast-iron cover.
- Roadside ditch on a slope → concrete trays (lotki) with an anti-scour outlet.
- Highway culvert → box collector, or large-diameter HDPE corrugated pipe as an alternative.
- Garden inspection point → plastic chamber + A15/B125 cover.
GON's combined offer
GON supplies concrete manholes, trays and collectors together with ductile-iron covers, rain gratings and HDPE corrugated pipe. The whole storm or sewer package can then be planned around a single delivery schedule for road and district projects.
Related products: Manholes & covers · D400 sewage manhole cover · Drop-in collar cover D400 DN860 · Road infrastructure
Further reading: Telescopic vs fixed frames
Get a project quote
Send chamber schedules and depths to sales@gon.ge or call +995 595 818 800.
GON supplies drainage, water, gas and road-infrastructure products to contractors, utilities and IFI-funded programmes across Georgia.