How a simple change to the treatment process can dramatically improve borehole water quality and protect expensive filtration equipment.
Private borehole water supplies can provide an excellent source of clean, reliable water for homes, farms and holiday accommodation. However, changing weather patterns and prolonged periods of heavy rainfall can dramatically alter the quality of untreated groundwater.
Recently we were contacted by the owner of a sheep farm and holiday cottages who had exactly this problem.
Although the treatment system had worked well for many years, increasingly frequent heavy rainfall events had begun overwhelming the filtration equipment, resulting in discoloured water and failed water quality tests.
This case study explains what happened, why it happened, and how we recommended solving the problem.
The Customer's Existing System
The property is supplied entirely from a private borehole and serves both the farmhouse and several holiday cottages.
The treatment system consisted of:
-
Borehole and jet pump
-
pH correction vessel
-
Turbidex sediment filter
-
Water softener
-
Twin jumbo sediment filters
-
UV disinfection system
For many years this arrangement provided satisfactory water quality.
However, after several periods of exceptionally heavy rainfall, things began to change.
The Symptoms
The customer contacted us after noticing:
-
Brown discoloured water returning.
-
Sediment cartridges blocking much more quickly.
-
The Turbidex media becoming compacted.
-
Poor backwashing.
-
Water remaining coloured even after treatment.
The local authority also sampled the water, with failures for:
-
Iron
-
Aluminium
-
Turbidity
-
Colour
The customer had already repacked the pH correction vessel previously, but the improvements only lasted a short time before the water quality deteriorated again.
The Water Analysis
A fresh laboratory analysis confirmed our suspicions.
Untreated Borehole Water
| Parameter | Result | UK Standard |
|---|---|---|
| Iron | 2.3 mg/L | 0.2 mg/L |
| Aluminium | 1.4 mg/L | 0.2 mg/L |
| Manganese | 0.068 mg/L | 0.05 mg/L |
| pH | 6.3 | Ideally above 6.5 |
| Nitrate | 24 mg/L | 50 mg/L |
The results showed that the water was carrying extremely high levels of iron and aluminium, together with elevated manganese and acidic pH.
While none of these values were impossible to treat, they placed a tremendous burden on the existing filtration system.
Why the System Began to Fail
Many people assume that if a filter stops working, the filter itself has failed.
In this case, that wasn't true.
The real problem was what was happening before the water even reached the filters.
During prolonged rainfall, surface water was carrying large quantities of fine silt, iron and aluminium into the borehole.
Once pumped from the ground:
-
dissolved iron oxidised
-
aluminium formed fine suspended particles
-
silt remained suspended
Instead of arriving as relatively clean groundwater, the Turbidex filter was being asked to remove huge quantities of suspended solids.
Eventually the media became coated with sludge.
Backwashing could no longer clean it properly.
Water found channels through the compacted media instead of flowing evenly through the filter bed.
Once channeling begins, filtration performance rapidly declines.
The Knock-On Effect
Once the Turbidex stopped removing suspended solids effectively, everything downstream suffered.
The contaminated water continued into:
-
the water softener
-
the pH correction vessel
-
sediment cartridges
-
UV steriliser
Iron can foul softener resin, reducing its exchange capacity.
Silt contaminates pH correction media, reducing its efficiency.
Finally, coloured water dramatically reduces UV effectiveness because ultraviolet light cannot penetrate turbid water effectively.
The entire treatment system was effectively fighting a losing battle.
Why Simply Replacing the Media Isn't Enough
Replacing the Turbidex media would certainly restore performance.
However, unless the incoming contaminant load was reduced first, exactly the same problem would return after the next period of heavy rainfall.
Rather than continually replacing expensive filter media, we looked at preventing the contamination reaching the filters in the first place.
The Recommended Solution
Instead of relying solely on filtration, we recommended introducing a settlement tank before the treatment equipment.
The proposed arrangement is:
Borehole → Settlement Tank → Existing Pump & Pressure Vessel → Turbidex Filter → Water Softener → pH Correction Vessel → Twin Sediment Filters → UV Disinfection → Property
The settlement tank performs several important jobs.
1. Slows the Water Down
Rather than flowing directly into the treatment plant, the water enters a large tank where velocity is dramatically reduced.
This gives heavier particles time to settle naturally.
2. Aerates the Water
By introducing the incoming water through a splash plate or spray nozzle, dissolved iron is exposed to oxygen.
The iron oxidises into solid particles which then settle to the bottom of the tank instead of passing into the filters.
3. Floating Suction Outlet
Rather than drawing water from the bottom where sediment collects, a floating intake always draws the cleanest water from just below the surface.
4. Sludge Removal
A large drain valve at the bottom of the tank allows accumulated iron sludge and silt to be flushed away after heavy rainfall.
Instead of blocking expensive filter media, the contamination is simply drained to waste.
Additional Recommendations
While refurbishing the system we also recommended:
-
Repacking the Turbidex filter with fresh media.
-
Replacing the pH correction media.
-
Inspecting and likely replacing the softener resin due to iron fouling.
-
Continuing regular sediment cartridge replacement.
-
Annual UV lamp replacement.
Why This Approach Works
Adding settlement before filtration dramatically reduces the work the filters have to perform.
Benefits include:
-
Longer Turbidex media life.
-
Improved backwashing.
-
Reduced cartridge consumption.
-
Better UV performance.
-
Less maintenance.
-
More consistent water quality throughout the year.
-
Greater resilience during periods of heavy rainfall.
Instead of treating the symptoms, the treatment system is protected from the source of the problem.
Final Thoughts
This case highlights an increasingly common issue with private water supplies.
As weather patterns become more extreme, many boreholes that historically produced good-quality water are now experiencing seasonal spikes in iron, manganese and suspended solids.
The answer isn't always larger filters or more treatment equipment.
Sometimes the most effective solution is allowing nature to do part of the work first.
By slowing the water down and allowing heavy contaminants to settle naturally before filtration begins, expensive treatment equipment can continue operating efficiently for many years.
If your borehole water becomes discoloured after heavy rainfall, your filters require increasingly frequent replacement, or your treatment system no longer performs as it once did, it may be time to review the overall process rather than simply replacing media.
At GAPS Water Treatment, we specialise in designing complete borehole treatment systems tailored to individual water analyses and site conditions. By understanding the chemistry of your water and how it changes throughout the year, we can recommend solutions that deliver reliable, long-term performance rather than temporary fixes.