When you rely on a private water supply—whether it’s a borehole, spring, or well—you aren't just a homeowner; you’re the manager of your own mini-utility company. Unlike city mains, where the water board handles the "push," your system’s performance depends entirely on how you manage Pressure Loss.
If your borehole pump is working hard but your taps are barely trickling, or if your UV filters keep alarming due to low flow, the culprit is almost certainly friction.
1. The Diameter Dilemma: Why One Size Doesn’t Fit All
In a borehole system, the water often travels a long distance from the pump to the holding tank, and then to the filtration system. Choosing the wrong pipe diameter is the most common cause of system failure.
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The "Choke" (Pipe too small): If you use narrow pipe (like 15mm or 20mm MDPE) for a long run from a borehole, the friction becomes a wall. The pump has to work at a much higher pressure to overcome this, leading to premature pump failure and massive electricity bills.
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The "Sludge" (Pipe too large): While larger pipes have less friction, if the pipe is too wide for the flow, the water velocity drops too low. In private supplies, this allows minerals (like iron and manganese) to settle and coat the inside of the pipe, eventually narrowing the passage anyway.
The Pro Tip: For most private residential supplies, 25mm or 32mm MDPE is the standard for the "rising main" (from the pump) to ensure a balance of low friction and healthy velocity.
2. The Friction "Thieves" in Your Filter Room
Private water supplies require more equipment than mains water—sediment filters, pH correction, carbon vessels, and UV sterilisers. Every one of these "stops" steals pressure.
Plumbers use "Equivalent Pipe Length" to calculate this. It treats every bend and valve as if you added several metres of extra pipe to your system.
Pressure Loss Reference Chart (Private Supply Standards)
| Component / Fitting | Equivalent Length (Add to your pipe run) | The "Why" |
| 90° Elbow (25mm MDPE) | + 0.8m | Sharp turns create high turbulence. |
| Tee-Junction (Branch) | + 1.5m | Dividing flow causes a massive energy drop. |
| Check Valve (Non-Return) | + 3.0m to 5.0m | The spring inside fights the water flow. |
| 20" Big Blue Filter | Variable (High) | Clean filters lose some; dirty filters lose everything. |
| UV Steriliser | + 2.0m to 4.0m | The narrow chamber creates a bottleneck. |
| Partially Closed Valve | + 10.0m+ | The single biggest cause of "mysterious" pressure loss. |
3. Splitting the Line: Filtration vs. Irrigation
A common setup in borehole systems is splitting the line after the pressure tank: one side goes to the house (filtered) and the other goes to the garden or livestock (unfiltered).
What happens at the split?
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Velocity Surge: When both sides are used at once, the water in the main pipe before the split has to move twice as fast. Friction loss doesn't just double; it quadruples.
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Pressure Robbery: The unfiltered garden tap has almost no resistance. Because water takes the path of least resistance, opening the garden tap can "starve" your house filtration system, causing the UV unit to overheat or the flow to drop to a crawl.
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The Fix: Always install a Pressure Sustaining Valve or ensure your main manifold is significantly larger (e.g., 32mm) than your branch lines (22mm or 25mm).
4. Summary: Optimising Your Private Supply
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Size for the Long Run: If your borehole is 50+ metres from the house, go up one pipe size to compensate for the distance.
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Minimize Bends: Use long-radius bends or flexible MDPE rather than sharp 90° plastic elbows to keep flow laminar (smooth).
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Monitor Your Filters: A pressure gauge before and after your filtration rack is essential. If the "gap" between the two gauges grows, your filters are clogged and "stealing" your pressure.
The Golden Rule of Boreholes: Your pump provides the pressure, but your pipework determines how much of it you actually get to use.
Borehole & Private Supply: The "Healthy Flow" Maintenance Checklist
When you manage your own water supply, your pump and filtration system are the heart of your home. Use this 5-point checklist every 6 months to ensure your system is running efficiently and your pipes aren't being "strangled" by hidden issues.
1. The "Delta P" (Pressure Drop) Test
If you have pressure gauges installed before and after your filtration rack (and you should!), check the difference between them while the water is running.
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The Goal: A difference of less than 0.5 Bar.
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The Red Flag: If the gap is 1.0 Bar or higher, your filter media (sediment or carbon) is clogged. Your pump is working twice as hard to "shove" water through a brick wall.
2. Check the Pressure Tank "Drawdown"
Your pressure tank (the big blue or red vessel) protects your pump from "cycling" (turning on and off too fast).
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The Test: Turn on a tap and time how long the pump stays off before it kicks in.
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The Red Flag: If the pump clicks on immediately every time you open a tap, the internal bladder has likely failed or lost its air charge. This "short-cycling" will burn out a borehole motor in months.
3. Inspect the Non-Return (Check) Valve
These valves ensure water doesn't flow backward into the borehole when the pump stops.
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The Test: Watch your pressure gauge when no water is being used.
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The Red Flag: If the pressure slowly drops while all taps are off, your check valve is leaking. Your pump is essentially re-pumping the same water over and over again, wasting electricity and increasing pipe wear.
4. Monitor for "Scale Strangling"
Private supplies often have high mineral content (iron, manganese, or calcium). Over time, these minerals plate the inside of your pipes.
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The Test: Compare the flow rate at the tap closest to the pump vs. the tap furthest away.
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The Red Flag: If the "far" tap has significantly lower flow than it did last year, your pipes may be narrowing due to scale. This increases velocity and friction, making your system increasingly inefficient.
5. The Visual Leak & Vibration Audit
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The Test: Walk the line from the borehole head to the filtration room.
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The Red Flag: Listen for "hissing" or look for damp patches. Even a tiny leak in a 25mm MDPE pipe creates turbulence that disrupts the flow and pressure for the entire house.
Pro Tip for Borehole Owners: Keep a "System Log." Write down your "10-Litre Bucket" fill time today. If it takes 30 seconds today but 50 seconds in six months, you’ve caught a problem before it became a crisis.
Download a copy of our PRIVATE WATER SUPPLY SYSTEM PERFORMANCE & MAINTENANCE GUIDE