Downpipes and stormwater drains carry water safely away from your home. When they fail, foundations, walls, and landscaping suffer.
Your roof collects every drop of rain that falls on it. For a 200m² roof in a 50mm rainfall event (common during Central Coast storms), that's 10,000 litres of water that needs to go somewhere — fast.
The system works in sequence:
1. **Gutters** collect water from the roof surface and channel it to downpipe locations 2. **Downpipes** carry water vertically from gutter level to ground level 3. **Stormwater drains** (underground pipes) carry water from the base of downpipes to the street drainage system or an approved discharge point
When any part of this chain fails — undersized gutters, blocked downpipes, collapsed stormwater drains — water overflows and damages your property. Foundation erosion, rising damp, flooded subfloors, and landscape washout are all consequences of failed stormwater management.
**Blocked downpipes:** Leaves, tennis balls, bird nests, and accumulated debris block downpipes, causing gutters to overflow. Signs: water pouring over gutter edges during rain, gurgling sounds from downpipes, or no water exiting at the base during rain.
**Undersized downpipes:** Older homes often have 65mm round downpipes that cannot handle modern rainfall intensity. Australian Standard AS/NZS 3500.3 now specifies minimum 90mm round or 100x50mm rectangular downpipes for most residential applications.
**Disconnected stormwater:** Downpipes that discharge onto the ground surface (rather than into underground drains) cause erosion, foundation damage, and neighbour disputes. Many older homes were never connected to council stormwater.
**Collapsed stormwater drains:** Old earthenware or PVC stormwater pipes collapse under driveways, from tree root invasion, or simply from age. Signs: pooling water in the yard, soggy patches that never dry, or sinkholes appearing along drain lines.
**Incorrect fall:** Stormwater pipes must maintain adequate fall (minimum 1:100 gradient) to flow by gravity. Settlement, root invasion, or poor original installation can create low points where water pools and sediment accumulates.
Correct downpipe sizing prevents overflow during heavy rain. The calculation considers:
• Roof catchment area draining to each downpipe • Local rainfall intensity (varies by region — Central Coast uses 175mm/hr for design purposes) • Gutter capacity and fall • Number of bends in the downpipe run
**General sizing guide (residential):** • 65mm round downpipe: handles up to 40m² of roof area • 90mm round downpipe: handles up to 80m² of roof area • 100x75mm rectangular: handles up to 100m² of roof area
**Common undersizing scenario:** A home with 200m² of roof area and only 2 downpipes (one each side) needs each downpipe to handle 100m² — requiring minimum 100x75mm rectangular or 90mm round. Many older homes have 65mm round downpipes in this configuration, which overflow in any rain event exceeding 20mm/hr.
**Our approach:** When we identify undersized downpipes during a roof or gutter inspection, we recommend upgrading to compliant sizes. This is often done during gutter replacement and adds minimal cost to the project.
In NSW, all properties are required to connect roof drainage to the council stormwater system where available. Discharging stormwater onto neighbouring properties or public footpaths is not permitted.
**Connection options:** • Direct connection to council stormwater pit in the street • Connection to council kerb outlet (charged connection through the kerb) • On-site absorption trench (where council stormwater is not available) • Rainwater tank with overflow to stormwater (increasingly common)
**Common issues we resolve:** • Homes never connected to stormwater (pre-1970s properties often discharge to surface) • Blocked connections that cause backflow and yard flooding • Illegal connections to sewer (stormwater must never connect to sewer) • Properties where development has changed drainage patterns
**Cost guide for stormwater connection:** • Connection to existing council pit (short run): $1,500–$3,500 • New stormwater line to street (15–25m): $3,000–$7,000 • Absorption trench (rural/no council stormwater): $2,000–$5,000
We hold the appropriate plumbing and drainage licences to install and connect stormwater systems in compliance with AS/NZS 3500.3 and local council requirements.
Preventative maintenance avoids expensive emergency repairs:
**Every 6 months:** • Clear gutters of leaves and debris • Check downpipe outlets are clear and flowing • Remove any debris from stormwater pit lids
**Annually:** • Flush downpipes with a hose to clear accumulated sediment • Lift stormwater pit lids and clear any debris or silt • Check for tree root intrusion at pit connections • Inspect for erosion around discharge points
**After major storms:** • Check all downpipes are still connected and flowing • Look for new pooling areas in the yard (may indicate collapsed drain) • Clear any debris washed into stormwater pits
**Leaf guard solutions:** For properties with significant tree coverage, gutter guard and downpipe leaf diverters significantly reduce maintenance frequency. We install several gutter guard systems and can recommend the best option for your tree type and gutter profile.
We offer scheduled gutter and stormwater maintenance — particularly valuable for investment properties, elderly homeowners, and commercial buildings where regular access is difficult.
Common causes: collapsed or blocked stormwater drain, insufficient drainage capacity, incorrect ground levels directing water toward the house, or no stormwater connection at all. We can CCTV inspect underground drains to identify the exact issue.
Yes, tree roots are the most common cause of stormwater drain blockage and collapse. Roots enter through joints in older earthenware pipes and can completely fill the pipe. Solutions include root cutting, pipe relining, or replacement with modern PVC.
You need a plumbing permit (Section 68 approval in NSW) to connect to council stormwater infrastructure. We handle the application process as part of the installation. The permit ensures the connection meets council standards and is recorded on your property's drainage plan.
If your gutters overflow during moderate rain (not just extreme storms), your downpipes are likely undersized. Other signs: water shooting out of gutter joints, persistent overflow at specific points, or gutters that fill faster than they drain. We can assess and recommend upgrades.
Stormwater Problems? We'll Sort It
From blocked downpipes to full stormwater connections — licensed drainage work across the Central Coast, Sydney, and Newcastle.