💧 Water Systems

1. Rainwater Harvesting

Rainwater harvesting is the fastest win in any water-independence system. A standard UK roof collects extraordinary volumes — with virtually zero infrastructure if you have a barrel and a gutter.

Yield Calculation

At 20 L/day per person, a 100m² roof supports 7–8 people year-round in the UK — even accounting for dry spells.

Catchment Surface Types

Guttering System

• Gutter sizing: 100mm half-round handles 50m² of roof. 125mm handles up to 100m². For larger roofs, run two separate downpipes.
• Slope: 1:500 minimum fall (2mm per metre). Too flat = standing water and mosquito breeding. Too steep = water overshoots bends.
• Materials: UPVC (standard), cast iron (long-lasting, heavy), or improvised: split bamboo, halved plastic bottles taped end-to-end, folded sheet metal.
• Leaf guards: Clip-in mesh guards over the gutter mouth, or a simple 2mm steel mesh cone over the downpipe inlet. Clean monthly in leaf-fall season.
• Downpipe diversion: A simple threaded diverter valve (or improvised T-junction with a cap) switches flow between the sewer and your storage tank. First flush should always go to drain.

Ground-Level Collection Without Gutters

If guttering is unavailable or the roof is inaccessible:

• Tarp funnel: 4×4m tarp on a frame angled to a central hole — funnels into a barrel below. Yields ~10L per mm of rain over 16m².
• Fog collection: In coastal/highland areas, a vertical mesh screen (1m²) can yield 3–10 L/day from fog condensation. Use shade cloth (20% UV) stretched on a frame above a trough.
• Dew collection: Polythene sheets staked flat on the ground, angled to a collection point. Most effective in arid zones with large day/night temperature swings.

2. Tank Construction & Storage

Water Requirements — How Much to Store

Target: store at least 90 days of comfortable use for your group. This protects against seasonal dry spells and equipment failures.

IBC Totes (Intermediate Bulk Containers)

The fastest and most cost-effective storage for most situations. 1,000L capacity, UV-stabilised, food-grade, stackable, and available second-hand for £30–60 each.

• Source: Ex-food-industry IBCs (check they previously held food-grade products only — avoid chemical IBCs even if "cleaned"). Look for IBCs marked "food grade" or "UN31A".
• Cleaning: Rinse three times with clean water. For chemical IBCs, reject entirely — residues are near-impossible to remove fully.
• Connection: Standard IBC outlet is 2" BSP male — connect with a 2" BSP female ball valve and 25mm poly pipe using a brass compression fitting.
• Cover: Keep lids on and block any light — algae growth is avoided entirely by keeping the interior dark.
• Freeze protection: Bury to 600mm below surface, insulate with straw bales, or move inside. Water expands 9% on freezing — a sealed full IBC can crack.

Ferrocement Tank (~£50 for 1,000L)

A permanent, extremely durable tank built from a chicken-wire frame plastered with cement. Outlasts plastic by decades and can be built to any size.

Buried Cistern

For large volumes (5,000L+) or where surface space is limited, a buried cistern is ideal. Keeps water cool (reduces algae/bacteria growth), frost-protected, and hidden.

• Construction: Excavate 20% larger than finished tank size. Construct with 200mm concrete block walls, reinforced with 10mm rebar in each course. Render interior with 3 coats of waterproof cement render.
• Cover: 200mm reinforced concrete slab with inspection access. Must support the weight of soil above plus foot traffic.
• Ventilation: Install two 40mm pipes through the lid, bent downward externally with fine mesh over the opening. Prevents insect ingress, allows pressure equalisation.
• Overflow: Pipe overflow to a soak-away or secondary storage at minimum — never let overflow pond near the tank foundation.
• Pump access: A 12V submersible pump (the type used for garden fountains) works perfectly for lifting water from a buried cistern. Suspended on a rope with the power cable protected by conduit through the lid.

3. First Flush Diverters

The first water off any roof after a dry period carries the highest contamination: accumulated bird droppings, dust, insect remains, leaf debris, and atmospheric pollutants. The first flush diverter discards this water automatically and is the single most important water quality intervention in a rainwater system.

How It Works

A standpipe fills with the first rainfall before the clean water reaches your tank. A slow-draining ball or simple hole at the base empties the standpipe between events, resetting it automatically.

Sizing

• Rule of thumb: Divert 1 litre per 10 m² of roof area per flush event.
• 100 m² roof: First flush volume = 10 litres. Use 110mm pipe, 1.05m length (holds exactly 10L).
• 50 m² roof: 5 litres. Use 110mm pipe, 525mm length, or 75mm pipe, 1.13m length.

Standard T-Junction Design (Simplest)

Ball-Float Upgrade

Replace the drain hole with a rubber ball that floats up as the standpipe fills, sealing the standpipe outlet and diverting all subsequent flow to the tank. More reliable in heavy continuous rain — prevents the 3mm hole from filling before the standpipe is full. Use a 25mm rubber ball in a 32mm socket at the base of the standpipe.

Additional Pre-Tank Filters

• Leaf trap: A mesh basket (3mm stainless mesh) inside the inlet to the tank — catches leaves, insects, and large debris. Clean monthly.
• Calmed inlet: Pipe the inlet to the bottom of the tank (not the top) to prevent disturbing sediment when refilling. Fit a T at the bottom so water exits sideways.
• Calmed outlet: Draw water from 150mm off the bottom of the tank — leaves the sediment layer undisturbed. A ball float on a pipe keeps the inlet 150mm below the surface regardless of water level.

4. Gravity Distribution Systems

No pumps. No electricity. Water at pressure — just by raising your tank above the point of use. Every metre of head (height difference between tank water surface and outlet) provides approximately 0.1 bar (10 kPa) of pressure.

Head Pressure Reference

Pipe Sizing

Frost Protection

• Bury all outdoor pipes to at least 600mm below ground level (below the UK frost line).
• Above-ground sections: Wrap with 25mm foam pipe lagging plus a layer of hessian sacking. In hard frosts, cover with straw bales overnight.
• Tank: If above ground, insulate all sides with 100mm rigid polyiso board or wrap with multiple layers of polythene sheeting filled with straw. A partially buried tank (300mm into the ground) is far more frost-resistant.
• Drain-back: Install a drain valve at the lowest point of every exposed pipe run. In a hard freeze warning, drain the system. Water expands 9% on freezing — a sealed, full pipe will burst.
• Keep flowing: Water moving in a pipe is much harder to freeze than standing water. A slow trickle overnight through an outdoor tap prevents freezing in all but the hardest frosts.

5. Well Construction

A well gives access to groundwater that has been naturally filtered through metres of soil and rock — generally safer than surface water but still requiring testing and purification. Well construction is physical, labour-intensive, and potentially dangerous (cave-in risk). Never work alone in a well.

Hand-Dug Well

Suitable for water tables within 10–15m of the surface. Requires two people — one digging, one lifting spoil and watching for danger signs.

Hand Auger / Borehole

For deeper water tables (15–40m) or where physical digging is not practical. A hand auger kit (available second-hand or improvised from steel pipe with a welded helix) can bore a 100–150mm hole.

• Casing: Lower PVC or steel casing into the bore as you drill. Perforate the bottom 2m with 2mm slots (slot casing) to allow water ingress.
• Development: Once drilled, surge the well by rapidly plunging a tight-fitting plug up and down in the casing. This develops the well and clears the fine sediment that blocks the slots.
• India Mark II: The standard hand pump for boreholes up to 45m. Can be fabricated locally from 40mm steel pipe and a cylinder/piston assembly. Yields up to 16L/min with sustained pumping.

6. Water Testing & Purification

Testing

Field water test strips (available in any camping or aquarium store) can assess pH, nitrate, nitrite, and hardness. Coliform bacteria test kits (Wagtech, IDEXX) give a result in 24–48 hours and are the gold standard for well commissioning.

Purification Hierarchy

Always follow this sequence — do not skip steps. Each step improves efficacy of the next.

Improvised Bio-Sand Filter

A biosand filter uses a biological layer (schmutzdecke) that forms naturally on top of fine sand — this layer is what provides pathogen removal, not just the mechanical filtration. The filter improves over 3–4 weeks as the schmutzdecke matures.

• Container: Any container 30cm+ diameter, 90cm+ tall. A concrete box, a plastic barrel, even a large clay pot.
• Layers from bottom: 5cm coarse gravel → 5cm medium gravel → 10cm coarse sand → 50cm fine sand (0.15–0.35mm grain size — washed river sand).
• Outlet: A pipe through the container wall 5cm from the base, bent upward so the water level inside always stands 5–10cm above the top of the sand. This keeps the schmutzdecke moist.
• Flow rate: 0.1–0.4 L/min for a 30cm diameter filter. Too fast = poor filtration. Too slow = stagnation.
• Maintenance: When flow rate drops below 0.1 L/min, swirl the top 2cm of sand with clean water only. Never let the sand dry out — this kills the biological layer and resets the 3-week maturation cycle.

Well Chlorination (Shock Treatment)

When a well tests positive for coliform bacteria or after any flooding event:

1. Calculate well water volume: π × r² × water depth × 1000 (litres per cubic metre).
2. Add 250mL of 5% bleach per 1,000L of well water. Lower slowly into the well using a bucket on a rope, sloshing against the sides.
3. Pump the well several times to circulate through pipes and fittings.
4. Leave for 12–24 hours. Do not use during this period.
5. Pump continuously until chlorine smell is gone. Retest after 48 hours.

7. Irrigation Systems

Swale Systems (Passive Water Harvesting)

Swales are level trenches dug along the contour of a slope. They intercept surface water runoff and allow it to infiltrate the soil slowly, charging the water table and feeding trees planted on the downhill berm. The system requires no ongoing energy or management once established.

Setting Out Swales with an A-Frame Level

An A-frame level is a simple timber device that identifies the contour line — the line of equal elevation. Build one from three straight pieces of timber (legs ~1.5m, cross-piece at the midpoint), hang a plumb bob from the apex, and mark where the string hits the cross-piece on level ground. That mark is your true horizontal.

Gravity Drip Irrigation

From an elevated IBC at even 0.5m head, a drip system can water a substantial garden with zero energy. Standard 16mm drip tape with 200mm emitter spacing uses ~1.0 L/hour per metre of tape at 0.5 bar — extrapolate down for low-pressure systems.

• Header pipe: 25–32mm MDPE running from tank to the top of the garden area. One ball valve for each bed circuit.
• Drip lines: 16mm drip tape or 4mm micro-tube with emitters at each plant. Keep runs under 30m to maintain even pressure at low head.
• Filter: 120-mesh disc filter on the header — critical. Emitters have 0.5mm orifices that clog with particles larger than 0.08mm. Clean monthly.
• Timer: A simple mechanical water timer (clockwork, not electronic) can automate irrigation even off-grid. Set for early morning — less evaporation, less disease.
• Winterisation: Drain all drip tape before first frost. Roll and store inside or bury under mulch.

Ollas (Buried Clay Pot Irrigation)

Ollas are unglazed terracotta pots buried in the soil with their necks above ground. Water filled into the neck slowly seeps through the porous clay wall directly into the root zone — only where plants need it, only as fast as roots absorb it. Studies show 50–70% water reduction compared to surface irrigation, with better plant growth.

• Making ollas: Two unglazed terracotta pots (30–40cm diameter) joined at the rim with a waterproof clay/cement mix. One pot inverted over the other. Leave a small opening at the base of the upper pot for filling, or use the drainage hole of the base pot.
• Installation: Bury with only the neck above ground. Each olla irrigates a 60–90cm radius. Place 1–3 seedlings around each olla.
• Filling: Top up every 3–7 days depending on temperature and plant uptake. Add a small stone or lid to the neck to prevent mosquito breeding.
• Winter: Dig up and store dry — freeze-thaw cycles will crack buried terracotta.

8. Quick Reference Card