Plumbing and Drainage Design in Kenya
Plumbing and drainage design covers how clean water reaches every fixture, how hot water is produced, and how foul water and rainwater leave the building safely. Beaver Concepts designs these systems for homes, apartments and commercial buildings in Kenya, sized for the building's demand, the water source available, and whether the site connects to a sewer or needs an on-site solution.
Water supply and storage
In much of Kenya, piped supply is intermittent, and a building that depends on direct mains pressure runs dry when the supply does. Design therefore begins with the daily demand, based on the number of people and fixtures, and the reliability of the sources: piped supply, a borehole, rainwater harvesting, or a combination.
From there we size storage tanks, decide whether gravity feed or a booster pump set is needed, and route the pipework. Tank capacity is a trade-off. Too little and you run out during a supply interruption; too much and you pay for structure and space you do not use, and water can stagnate. We size it to how long the supply is typically off, not to a rule of thumb.
Drainage: sewer or on-site treatment
Where a public sewer is available, the design connects to it, subject to the water service provider's requirements. Many sites have no sewer within reach, so foul water must be treated and dispersed on site. The right solution depends on soil percolation, the water table, plot size and the number of users.
| Option | Used when | Points to weigh |
|---|---|---|
| Connection to public sewer | A sewer is available near the plot | Lowest on-site burden; needs the provider's approval, and connection cost depends on distance |
| Septic tank with soakaway | No sewer; soil drains freely; adequate plot size | Common and simple; needs a soil percolation assessment and periodic desludging; unsuitable near a high water table or boreholes |
| Biodigester or package treatment plant | No sewer; poor percolation or tighter plots | Treats more fully and can suit poor soils; higher first cost and needs operation and maintenance |
Rainwater, hot water and coordination
Stormwater from roofs and paved areas needs its own route. Sending it into the foul system overloads treatment, and letting it run onto a neighbour's land causes disputes. We design gutters, downpipes and soakpits or discharge routes, and where sensible provide for harvesting the roof water into a tank for garden or non-drinking use.
Hot water can come from electric heaters, solar water heaters or a heat pump, each with different running costs and installation demands. This choice interacts with the electrical design, since electric water heating is a large load, and with solar, so we coordinate them rather than decide each in isolation.
Pipes cross beams, walls and floors, so we coordinate routes with the structural engineer before construction. Retrofitting a drain through a beam is either impossible or expensive.
How plumbing and drainage works with us
- Stage 01
Demand and source assessment
We establish occupancy, fixtures, water sources and how reliable supply is at your site.
- Stage 02
Supply and storage concept
Storage size, pumping or gravity feed, and hot water approach are agreed with you.
- Stage 03
Drainage strategy
Sewer connection or on-site treatment is selected using site conditions and approval requirements.
- Stage 04
Detailed design
Pipe sizes, gradients, tank and chamber details are calculated and drawn.
- Stage 05
Coordination and specification
Routes are coordinated with structure and other services, and materials specified.
- Stage 06
Inspection and testing
Pipework is pressure tested and drains checked before they are concealed and before handover.
What you receive
- Water demand and storage calculations
- Cold and hot water supply layout drawings
- Foul and storm drainage layouts with levels and gradients
- Septic, soakaway or treatment plant design where required
- Tank, pump and plant details
- Specification and plumbing bill of quantities
- Pressure and drainage test records
Related services
- Borehole and water treatmentBorehole design and water treatment in Kenya: hydrogeological survey guidance, permits, pumping, storage and treatment matched to your water test results.
- Solar PVSolar PV design in Kenya: load analysis, system sizing, hybrid and off-grid options, batteries and specifications for homes, farms and businesses.
- Architectural DesignArchitectural design in Nairobi: house plans, 3D renders, interior design and county approvals for homes, apartments and commercial buildings.
Questions we are often asked
How big should my water tank be?
It depends on daily demand and how long your supply is typically interrupted. We calculate it from the number of occupants and fixtures and from the reliability of your supply, rather than using a standard size.
Can I use a septic tank in Nairobi?
Where there is no public sewer, a septic tank with a soakaway can work if the soil drains well and the plot has room. In areas with black cotton soil or a high water table it may not, and a biodigester or treatment plant may be better. A percolation test decides it.
Do I need a sewer connection approval?
Connecting to a public sewer needs the approval of the water service provider. We prepare the drawings and information they require as part of the design.
Is rainwater harvesting worth it?
Often, particularly where mains supply is unreliable. Harvested roof water suits gardens, cleaning and toilet flushing. It needs storage sized to your rainfall pattern and demand, and should not be used for drinking without treatment.
Should I use solar or electric water heating?
Solar water heating costs more to install but lowers running cost, and suits homes with steady hot water use. Electric heating is cheaper to install but adds a large electrical load. We compare them against your usage and electrical capacity.
Why does drainage design need to be done before construction?
Drains need continuous gradients and must cross structure. Routes and levels are cheap to plan on paper, and costly or impossible to fix after beams, slabs and walls are cast.
Last updated 29 September 2026
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