Underground and roof water tank leaks: how to read the signs and test your tank yourself
The tank level keeps dropping and the pump runs too often. Or the water bill went up and you don't know why, or the water suddenly tastes different. Many villa owners complain of these signs, and an underground water tank leak is one of the most common causes, because the tank is buried and out of sight.
In this guide you will learn how to tell a tank leak from a network leak, how to run a simple level test in one night, and how to use the Underground Tank Assessment tool to estimate the likelihood of groundwater or contaminated water getting into your tank. You will also learn when an electronic inspection becomes necessary.
What is an underground water tank leak, and what does this tool do?
A tank can leak in two directions. The first is water getting out through a crack in the wall or floor, or around the pipe openings, so you lose water you have paid for. The second is water getting in from outside, such as groundwater or a nearby sewage leak. The second is more dangerous because it affects the safety of your drinking water.
The Kashf Underground Tank Assessment focuses on the second direction. It is a 6-question survey that gives you a score out of 12 and a likelihood level (low, medium or high) of groundwater or contaminated water getting into your tank. Water getting out is found with the level test explained in this guide.
Many homes in Saudi Arabia, and in other hot, dry regions, store water in a ground tank, then pump it to a roof tank. That is why tank leaks matter so much there.
Who is this tool for?
- Owners of a villa or house with an underground tank, especially an old concrete one.
- Anyone who has noticed a change in the taste, smell or color of the tank water.
- Buyers or tenants who want a first estimate of a property's tank condition.
- Maintenance managers in a residential building who need to prioritize inspections.
When should you use it?
- When the tank level drops more than your consumption explains.
- When the water's taste or smell changes, or it turns cloudy.
- After heavy rain, or when the groundwater level rises in your area.
- If more than a year has passed since the tank was last cleaned or checked.
- Before buying a property, or before having the tank re-waterproofed.
Where do you use it?
Open the tool from the Tools Hub on your phone or computer; no sign-up is needed. It works anywhere. Ideally, answer standing next to the tank, so you can see its cover and surroundings and know where the nearby drain line or inspection chamber is.
The level test is done on site, at the opening of the ground tank or the roof tank.
What do you need before you start?
- A rough idea of the tank's age and material (concrete, fiberglass or plastic).
- The date it was last cleaned, disinfected or checked, if known.
- A flashlight to see the tank walls from the opening, without climbing in.
- For the level test: tape or a marker, a ruler or tape measure, and a night with no water use.
How to use it correctly, step by step
Underground Tank Assessment
A scored survey of 6 questions about the underground tank: its age, its material, any visible cracks, how close it is to a sewage line or rainwater path, when it was last checked or disinfected, and any change in the water's taste, smell or color.
Each question has 3 options worth 0, 1 or 2 points depending on risk. The tool adds the points to give a score out of 12, and the result appears automatically after you answer the last question. The calculation runs in your browser only, and your answers are not sent anywhere.
Ask about your tank: after the questions there is a section called "Ask about your tank or attach a photo". It gives advice consistent with the assessment result, with an optional photo of the tank, float valve or crack. This section only appears when AI analysis is switched on for the site. If it is unavailable or reaches its limit, the tool keeps working on its fixed rules, with a small note.
Steps for correct use
- Open the tool
Go to the Tools Hub, choose the "Underground Tank Assessment" card and open it. The six questions appear with a progress bar showing "0 of 6 questions".
- Answer age and material
For age, choose "Less than 5 years", "5 to 10 years" or "More than 10 years". For material, choose between "Fiberglass / leak-proof plastic", "Concrete with good waterproof lining" and "Old concrete with no visible waterproofing". If you are not sure about the lining, choose the worse option.
- Check for cracks and surroundings
Look at the cover, the neck and the walls you can see with the flashlight. Then say how close the tank is to a drain inspection chamber or rainwater path: "Relatively far", "Moderately close" or "Very close or touching".
- Answer on maintenance and water
Choose when the tank was last checked or disinfected: within the last year, "1 to 3 years ago", or "I don't know / never". Then answer about changes in taste, smell or color: "No", "Sometimes" or "Yes, clearly".
- Read the result and decide
After the sixth question, the score out of 12 appears with the likelihood level and advice. You can change any answer by tapping another option, and the result recalculates instantly.
- Ask the AI (optional)
Describe what you notice (such as how much the level drops overnight) or attach a photo in the AI section, then tap "Ask".
How to read the result
- Low likelihood (0 to 4 out of 12): no clear risk factors. Keep up cleaning and a regular check every one to two years.
- Medium likelihood (5 to 8 out of 12): several factors raise the chance of groundwater or contaminated water getting in. The tool recommends an electronic inspection and disinfection soon, to confirm your drinking water is safe.
- High likelihood (9 to 12 out of 12): do not delay the inspection. The tool advises you to stop using the tank water for direct drinking until you have confirmed it is safe.
The score measures risk factors; it does not prove a leak. A new tank can leak because of a workmanship fault, and an old tank can be sound. Confirmation comes from the level test and then an on-site inspection.
- AI reply: practical steps and urgency consistent with the assessment result; if it sees something that contradicts the result, it tells you so clearly.
Signs of an underground or roof tank leak
Underground tank signs
- The pump runs more than usual, or at night while everyone is asleep.
- The level drops during hours when no water is used.
- Damp, salt deposits or sunken tiles or ground around the tank.
- A higher water bill without higher consumption.
- Cloudiness, an odor or a strange taste, which may mean water is getting in from outside.
Roof tank signs
- Water running constantly from the overflow pipe, usually because the float valve does not close fully.
- Damp stains on the ceiling of the room under the tank, or peeling paint on the wall next to it.
- Leaks at the inlet and outlet joints or at the valve.
- Very hot water in summer, which is an insulation problem, not a leak.
The level test: how to check for yourself that the tank is leaking
In Saudi Arabia, water usually flows like this: public mains, then the meter, then the ground tank, then the booster pump, then the roof tank or straight into the house. So you need to isolate the tank from its inflow and outflow before judging it.
- Fill the ground tank until the float valve shuts.
- Close the inlet valve after the meter and switch off the pump's power so it does not draw water.
- Mark the water level with tape or a marker and note the time.
- Wait 6 to 12 hours with no water use; overnight is ideal.
- Measure the level again.
- The level dropped: water is escaping through the tank walls, the floor or the suction pipe opening.
- The level rose with the valve closed: either the valve does not seal, or water from outside is getting into the tank. This needs an urgent inspection.
- No change: the tank is probably sound. Look for the leak after the pump, in the house network.
Do the same for the roof tank: switch off the pump, close the outlet valve to the house and watch the level. To test the line between the meter and the tank, use the meter test; the details are in the water meter leak test guide.
Why do tanks leak so often in Saudi homes?
- Old concrete tanks were often built without proper internal waterproofing, and over the years shrinkage and settlement cracks appear.
- Summer heat makes concrete expand and contract, widening fine cracks and wearing out the float valve and joints in the roof tank.
- Proximity to drain inspection chambers in small yards raises the risk of contamination if a crack appears.
- Areas with high groundwater put pressure on the tank walls from outside.
That is why the tank should be cleaned and disinfected regularly, and waterproofed inside only with a material made for contact with drinking water, not any general-purpose product.
Common mistakes that spoil the result
- Leaving the pump on during the level test. The pump draws water, so you think the tank is leaking.
- Forgetting the float valve. If you do not close the inlet valve, the float valve may replace lost water, so the tank looks sound while it is leaking.
- Testing while water is in use. A running washing machine or a filling water heater is enough to spoil the measurement.
- Optimistic answers in the survey. "Not sure" about cracks is not "No".
- Climbing into the tank without precautions. A tank is a confined space, and its air may be stale or full of cleaning fumes.
- Patching a crack with a general waterproofing product. The material must be safe for contact with drinking water.
Honest limits of the tool
- The survey estimates risk factors from your answers. It does not measure the water or see inside the tank.
- The tool is designed for underground tanks and water getting into them. Water getting out of the tank, or roof tank problems, are found with the level test and an on-site inspection.
- The result does not locate a crack or show its size.
- Drinking water safety cannot be decided by taste and smell. If you suspect contamination, stop drinking from the tank until it has been cleaned, disinfected and tested.
- Large cracks or settlement in the tank structure are a structural matter for a licensed engineer.
When do you need a leak detection technician?
Ask for a professional inspection if:
- The survey result is "medium" or "high".
- The level dropped or rose during the overnight test even with the valve closed.
- The water's color or smell changed.
- There is damp or settlement around the ground tank, or under the roof tank.
With the tank leak detection service, the Kashf team inspects the ground and roof tanks inside and out with electronic equipment, without demolition, and finds whether the loss comes from the tank itself or the lines connected to it. Cracks are treated with epoxy made for drinking water, and you receive a written technical report. The price is set once your case is known; see the leak detection cost guide. On-site service is available in Saudi Arabia only.
Frequently asked questions
How do I know if my underground water tank is leaking?
Close the inlet valve after the meter, switch off the pump's power, mark the water level, then wait 6 to 12 hours with no water use. If the level drops, the tank is losing water through its walls, floor or openings. If it stays the same, look for the leak in the house network after the pump.
Why does the pump run at night while everyone is asleep?
Usually water is being lost somewhere. It could be a leak in the roof tank or in the lines after the pump, a float valve that does not close so water escapes from the overflow, or a pump valve letting water flow back. Check the overflow first, then run the level test on each tank separately.
Does an underground water tank leak raise the water bill?
Yes. Water leaking from the tank came through the meter, so you pay for it. With tiered tariffs such as the Saudi NWC tiers, a continuous leak can push you into a more expensive tier. But a high bill alone does not tell you where the leak is; it could be on the line before the tank or in the house network.
The tank level rises even with the valve closed. What causes that?
Either the valve is faulty and does not seal, or water from outside is getting into the tank, such as groundwater or a sewage leak. The second possibility affects drinking water safety, so stop drinking from the tank and ask for an urgent inspection.
How often should I clean and disinfect the tank?
Once every 6 months is usual for household tanks, and sooner if you notice sediment or a change in the water. Cleaning is a chance to see the walls and floor and spot any cracks. Do not climb into the tank alone; use a specialist with ventilation and safety equipment.
Can the tank assessment tool confirm a leak?
No. The tool is a survey that estimates the likelihood of groundwater or contaminated water getting into your tank, based on its age, material, condition and location. It helps you set priorities, but confirmation needs a level test followed by an on-site inspection with electronic equipment.
What is the difference between a tank leak and a float valve leak?
A tank leak is water escaping through a crack in the wall or floor, or around the openings. A faulty float valve does not close when the tank is full, so the excess water runs out of the overflow pipe. A float valve is usually quick and easy to fix, but the waste is large if it continues for days.
Can I use any waterproofing material inside a drinking water tank?
No. Inside a drinking water tank you need a material that is made and safe for contact with drinking water, such as an epoxy rated for this use, and you should ask the supplier for proof. General-purpose materials can release odors or unsafe substances into the water.
How does a technician find a tank leak without breaking anything?
They start by isolating the tank from its inflow and outflow and measuring the level, then inspect the walls inside and out. They use acoustic sensors, thermal cameras and pressure testing on the connected lines to find whether the loss comes from the tank or the pipes before doing any work.
Related services
On-site inspections are available in Saudi Arabia; the tools and guides work anywhere.
This guide is educational. It explains estimation tools that help you understand a situation and decide what to do next; confirming a leak and pinpointing it always requires an on-site inspection with instruments. Structural questions are for a licensed engineer to decide.