Case Study: Water Tank & Sump Cleaning in HSR Layout, Bangalore

The Problem

A family in an HSR Layout independent house contacted LoklFix after their children had recurring stomach issues. Their doctor had asked them to check their drinking water source. The family had not cleaned their underground sump in 18 months — they thought annual cleaning was sufficient. WhatsApp TDS reading before cleaning: 890 ppm (WHO safe limit for drinking water: 500 ppm).

Our Diagnosis

Visual inspection of the sump (after dewatering) found a 3-4 cm thick layer of grey-brown sludge on the floor and walls — the accumulated sediment from 18 months of borewell water supply. The sludge was supporting bacterial biofilm growth visible as a slick coating on the walls. The borewell water feeding the sump had 600 ppm base TDS — the additional 290 ppm above baseline was from concentrated dissolved solids in the sludge layer being redistributed into the water.

The Solution

Full 7-step process: dewater completely with submersible pump, manual scrubbing of walls and floor, high-pressure wash, food-grade disinfectant application (30-minute dwell time), clean water rinse, UV sterilisation of refilled water, TDS measurement and WhatsApp report with before/after readings.

The Result

What This Job Cost — And Why

The total cost of ₹2,499 for this job breaks down as: 35–40% materials, 25–30% surface preparation and labour, 10–15% mobilisation and equipment. This is higher than the cheapest quotes the customer received — but it produced a permanent fix where two previous cheaper jobs had failed completely.

The framework for evaluating any waterproofing quote isn't price per sqft. It's: What is the contractor's diagnosis of the root cause? What preparation will they do? What material and how many coats? What does the written warranty cover? Get those four answers in writing before comparing quotes.

What the Sludge Contains — and Why It Matters

The grey-brown sludge found in the HSR Layout sump is not dirt — it is a biologically active layer. Under microscopic examination, tank sludge from Bangalore borewell-fed buildings contains:

• Mineral precipitates: Calcium carbonate, magnesium compounds, and iron deposits from the borewell water supply
• Biofilm colonies: Bacteria embedded in a protective polysaccharide matrix — standard chlorination at normal doses cannot penetrate mature biofilm
• Sediment particles: Fine clay and silt from the borewell aquifer, not filtered out by standard inlet screens
• Dead organic matter: Insects, leaves, and other debris that entered through uncovered or poorly covered tank access points

The family's recurring stomach issues were consistent with waterborne bacterial contamination — specifically, biofilm-associated bacteria like E. coli and Pseudomonas that thrive in sludge layers and are not killed by the concentration of chlorine normally present in borewell-distributed water.

The TDS Numbers — Explained

The pre-clean TDS reading of 890 ppm breaks down approximately as: 600 ppm from the borewell source water (baseline for this area) + 290 ppm from dissolved minerals in the sludge layer being redistributed into the water column. After cleaning removed the sludge, the borewell source TDS of approximately 180 ppm was the baseline — the sludge had been contributing 600+ ppm of additional dissolved solids.

For context: WHO guideline for acceptable drinking water TDS is 500 ppm. India's BIS standard is 500 ppm (relaxable to 2,000 ppm where no alternative is available). At 890 ppm, the family's water exceeded both standards significantly.

Recommended Cleaning Frequency for North Bangalore Borewell Areas