Technical Canlon| Professional Explanation of Canlon Roof Siphon Rainwater Drainage System

Siphon drainage working principle

The siphon phenomenon is a natural phenomenon in fluid mechanics. It utilizes the weight and pressure difference of the liquid itself to easily draw the liquid from a high place to a low place without the aid of an external pump.

Canlon's siphon roof drainage system relies on Bernoulli's fluid dynamics equations and is equipped with self-developed hydraulic calculation software to accurately match pipe diameter and number of ducts, ensuring stable siphon activation during extreme rainfall and forming full pipe flow. This is different from traditional gravity semi-pipe drainage and achieves rapid drainage.

1. Initial Gravity-Based Water Storage Stage

During light rain, rainwater flows into the gutters and is collected by Canlon's special siphon rainwater hoppers. The rainwater hoppers have built-in anti-vortex and air-barrier grilles to prevent large amounts of air from entering the pipes, and the roof continues to accumulate water to a critical depth of about 30-50mm.

2. Gas-water mixing transition stage

As rainfall increased, rainwater continued to flow into the pipes, and the high-speed water flow carried away the air inside the pipes, creating a mixed flow of air and water columns within the pipes.

3. Negative pressure siphon full flow stage (core operating condition)

Air is completely expelled, and the entire pipe is 100% pressurized. The negative pressure suction is created by the vertical height difference between the roof and the outdoor drainage outlet, and the flow velocity can reach 6-10m/s (compared to only 1-2m/s by traditional gravity). This high-speed suction of water from the roof prevents water from accumulating or overflowing during heavy rain.

Canlon siphon drainage complete set of components

1. Core Component: Canlon's proprietary siphon rainwater hopper (patented product)

• Features a layered air-barrier grille, anti-vortex guide vanes, and side water intake to prevent air from being drawn in;

• Compatible with metal composite tiles, TPO/PMP coated metal roofs, and concrete roofs; CTC certified by the National Inspection and Quarantine Bureau.

• The low water depth design in front of the gutter reduces the height of water accumulation in the gutter, thus reducing the roof load and the risk of leakage.

2. HDPE (High-Density Polyethylene) pipes and fittings

Canlon siphon drainage system uses brand new, anti-aging HDPE pipes, with hot-melt integrated welding for strong sealing; it is available in a full range of specifications from De63 to De315, and is resistant to high and low temperatures, acids and alkalis, making it suitable for complex working conditions in factories and stadiums.

3. Secondary energy dissipation suspension and fixing system (Canlon's patented bracket)

The high-speed water flow under siphon negative pressure will generate vibration. The suspension system composed of special square steel, threaded rod, anti-vibration pipe clamp, and strut clamp is used to dissipate the expansion and contraction and vibration load of the pipeline. Horizontal pipes do not need to be sloped and can be laid horizontally at will.

4. Auxiliary components

The system includes gutter overflow outlets, diversion connecting short pipes, outgoing conversion pipes, and outdoor energy dissipation inspection wells; it can be paired with Canlon rainwater harvesting modules to achieve rainwater recycling and reuse in sponge cities.

Comprehensive Analysis of the Advantages and Disadvantages of the Canlon Siphon System

(I) Core Advantages (Compared to Traditional Gravity Drainage)

1. Significantly improved drainage efficiency, eliminating water accumulation on the roof.

The full-pipe flow rate is 3 to 6 times that of a gravity system, and the drainage speed of heavy rain is increased by 70% for the same roof area; large-span factories and stadiums will not experience gutter overflow or roof flooding.

2. Smaller pipe diameter, saving 30%–50% on material usage.

Gravity systems typically use pipes with a diameter of De200 or larger, while Canlon siphon systems commonly use De75–De160. This reduces the number of pipes, fittings, and risers by half, significantly lowering material costs and transportation and hoisting expenses.

3. Horizontal pipes are laid with zero slope to maximize indoor net height.

Traditional gravity-fed horizontal pipes must slope down to 1‰–3‰, taking up ceiling height; Canlon siphon suspension pipes can be laid out completely horizontally, eliminating the need to lower ceilings in factories, shopping malls, and stadiums, thus freeing up usable indoor space.

4. Fewer rainwater inlets and downpipes significantly reduce potential leaks.

Large roof areas require only a few rainwater hoppers, reducing the number of gutters and roof waterproofing damage points. Combined with Canlon's own waterproof membrane, it achieves integrated waterproofing and drainage, reducing the risk of leakage from the source.

5. High-speed water flow self-cleaning, long-term maintenance-free operation.

High-speed water flow of 6-10m/s washes away mud, sand and fallen leaves from the pipe wall, making the pipe less prone to clogging. There is no need to install cleaning wells indoors, resulting in extremely low maintenance costs.

6. Flexible layout, adaptable to irregularly shaped and large-span roofs.

Unrestricted by building beams, columns, or steel structure layout, risers can be centrally arranged at the corners of buildings without disrupting the interior space layout; suitable for photovoltaic roofs, curved stadiums, and extra-long factories.

7. The system is durable, green, and low-carbon.

HDPE pipes have a service life of ≥25 years, matching the service life of metal roofs and waterproof membranes; they can be connected to rainwater harvesting modules, allowing rainwater to be recycled for landscaping and flushing, meeting sponge city standards and earning bonus points for green buildings.

(ii) System limitations

1. The initial design phase has a high barrier to entry, requiring specialized hydraulic modeling and calculation.

Piping and rainwater hoppers cannot be arbitrarily installed or added/removed on-site. The Canlon technical team needs to conduct in-depth hydraulic calculations on the drawings, which ordinary construction teams cannot design on their own.

2. The initial overall cost of a single system is slightly higher than that of a simple gravity drainage system.

Specialized rainwater hoppers and earthquake-resistant suspension supports cost more than ordinary gravity-fed components, but the savings in pipe materials and civil engineering ceilings can offset the price difference, resulting in a lower overall cost in the medium to long term.

3. High construction precision requirements

The levelness of the rainwater hopper, the hot-melt welding of the pipes, and the spacing of the supports must be strictly constructed in accordance with the specifications. Installation deviations will affect the formation of siphon negative pressure, and on-site guidance and instruction from Canlon Technology are required.

4. Very small roofs (under 1000㎡) generally offer poor value for money.

For small shops and small roofs, simple gravity drainage is more economical, while siphon drainage is more suitable for large-area, large-span buildings (over 5000㎡).

Mainstream application scenarios

1. Industrial plants/heavy equipment base (core scenario)

Steel structure ultra-long roofs, large-span workshops, and warehousing and logistics parks, such as combined factory buildings of more than 100,000 square meters, solve the problem of centralized drainage of large-area roofs.

2. Large public buildings

Convention centers, stadiums, high-speed rail stations, airport terminals, and subway stations, with curved/irregular roofs and ultra-high ceilings, require high levels of ceiling height and aesthetics.

3. Commercial complexes and shopping centers

The multi-story podium features a large roof and skylights, with horizontal pipes that are not sloped and do not lower the ceiling, ensuring the floor height of the shops.

4. Coated metal composite tile roofing

It is compatible with Canlon TMP/PMP metal composite tile integrated roofing, has exclusive testing patents, and provides complete waterproofing and drainage for metal roofing.

5. Photovoltaic integrated roof

Photovoltaic panels cover a large area of the roof, reducing the risk of waterproofing through openings, and simultaneously collecting and reusing rainwater.

6. Sponge City Supporting Projects

When paired with Canlon PP water storage modules, it achieves integrated rainwater drainage, storage, and utilization, making it suitable for resettlement housing, industrial parks, and schools.

Typical engineering cases

Yongda Chemical Machinery (Rudong) Heavy Equipment Production Base

• Project scale: Total construction area of 120,000 square meters, including combined factory buildings and special material factory buildings with extra-long steel roofs, with a total investment of 1 billion yuan;

• Solution: The entire roof will be equipped with the Canlon siphon rainwater system, with the technical team providing full-process drawing refinement, material supply, and on-site technical guidance;

• Implementation results: The number of rainwater hoppers and risers is reduced by 52% compared to the original gravity solution, the ceiling does not need to be lowered, nearly 40% of pipe materials are saved, there is no water accumulation or leakage during the rainy season, and it is suitable for the corrosion resistance requirements of chemical plant buildings.

Multi-regional metal composite tile roofing supporting projects

Based on Canlon's invention patent "Siphon Drainage Test Device for Coated Metal Roof", we provide complete siphon solutions for TMP/PMP integrated panel roofs in various regions, realizing integrated waterproofing and drainage construction, and avoiding the common problem of leakage in metal roof gutters.

Canlon's core differentiating advantages (industry comparison)

1. Synergistic development of waterproofing and drainage: We supply complete sets of waterproof membranes, metal roofing, and siphon systems with standardized components, eliminating leakage issues caused by connections between different brands;

2. A complete set of self-developed patents: multiple invention patents for rainwater hoppers, testing devices, and earthquake-resistant suspension systems;

3. Full-process technical services: Free hydraulic modeling, secondary refinement of drawings, on-site construction handover, and one-stop service for water supply acceptance;

4. Stringent testing exceeding national standards: Our own laboratory can simulate different rainfall, gutter cross-sections, and roof slope conditions to test the stability of the system.