An old water cistern can often be reused to collect rainwater, hold water for garden irrigation, or serve as a decorative feature. First identify what it is made of, check its condition and history, and confirm that your intended use is allowed and safe; never assume stored water is suitable for drinking.
What You’ll Need
- Work gloves, sturdy footwear, and eye protection
- A flashlight, camera, and notebook for inspection
- A stiff brush and a suitable cleaning tool for the cistern’s material
- A safe way to keep rainwater out while you inspect the interior
- Materials for your chosen use, such as a screened inlet, secure cover, overflow pipe, or irrigation hose
- Help from a qualified cistern, plumbing, or building professional if the structure is damaged, buried, or difficult to access
Step-by-Step
- Find out what the cistern was used for. Ask previous owners or check available property records, maintenance notes, and visible pipe connections. Look for clues such as an inlet from a roof drain, a pump connection, or plumbing that once supplied the building. A history of unknown chemicals, sewage, fuel, or other contamination is a reason to stop and seek expert advice before disturbing the tank. If its history cannot be established, limit plans to uses that do not expose people, animals, or edible plants to questionable water.
- Choose a realistic purpose. Common possibilities include capturing rainwater for ornamental planting, holding water for outdoor cleaning, or adapting the cistern as a non-water feature. Consider how water will enter, where overflow will go, and how the tank will be emptied and maintained. If you want drinking water, indoor plumbing, or water for edible crops, do not proceed on the assumption that cleaning alone makes the cistern suitable. Those uses need appropriate assessment, treatment, and compliance with local requirements.
- Check local requirements before changing connections. Rules can vary for rainwater collection, plumbing alterations, drainage, historic structures, and buried tanks. Contact the relevant local building or water authority if the cistern connects to household plumbing, a public water supply, a drain, or a septic system. Keep any existing potable-water pipes physically separate from reused cistern water unless an approved professional designs the connection. A simple hose or valve arrangement can still create a contamination risk if it allows water to flow back into clean plumbing.
- Inspect from a safe position. Look for cracks, leaning walls, loose masonry, corrosion, damaged liners, exposed reinforcement, and signs of movement. Check the rim and cover as well as the visible interior. Do not enter a cistern to inspect it: enclosed tanks can present serious hazards, including falls, poor air quality, and difficulty getting out. Do not lean over an unstable opening or remove a heavy cover alone. Photograph what you can see, and have a qualified professional inspect structural concerns or any tank that is hard to access.
- Make the area safe and control access. Keep children and animals away while the cistern is open or work is under way. Use a sound, secure cover that cannot be easily displaced, and ensure that any access opening is protected. If the tank is above ground, check that its base is stable and can support its contents; water is heavy, and a weakened support can fail. For a buried tank, do not dig beside it or load the ground above it until its construction and condition are understood.
- Remove debris without creating a new hazard. Clear leaves, sediment, and loose material only if you can do so safely from outside the cistern. Avoid pressure-washing or scraping an unknown lining, since this can damage it or spread contamination. Do not mix cleaning chemicals, and do not use household cleaners or disinfectants unless their suitability for the cistern’s material and intended use is established. If there is sludge, a strong unusual odor, suspected chemical residue, or a dead animal, stop and arrange an appropriate professional assessment.
- Repair the structure and fittings before collecting water. Have cracks, leaking joints, failed mortar, corroded fittings, or damaged liners evaluated and repaired with materials suitable for the tank. Do not cover a leak with a temporary patch and assume the cistern is sound. Confirm that the lid fits securely and that pipes and openings are protected from debris and animals. If repairs involve structural work, plumbing, or a buried tank, use a qualified professional rather than attempting an uncertain fix.
- Set up collection and overflow for the chosen use. For rainwater collection, route the intended inlet into the cistern and fit a suitable screen to reduce leaves and animal access. Provide an overflow route that carries excess water away from foundations, neighboring property, and areas where it could cause erosion or standing water. Keep roof runoff and cistern water separate from drinking-water plumbing. Do not direct overflow into a drain or other system unless that connection is permitted and appropriate.
- Test the system before relying on it. Introduce water in a controlled way and check visible joints, the base, and the overflow for leaks or unexpected pooling. Make sure water drains where intended and that the cover stays in place. If the water is cloudy, smells unusual, or shows an oily sheen, keep people and animals away from it and do not use it for gardening or cleaning until the cause is understood. A clear appearance does not prove water is safe to drink.
- Set a maintenance routine. Periodically inspect the cover, inlet screen, visible pipework, overflow, and surrounding ground. Remove leaves from screens and look for new cracks, leaks, or signs of animal access. Emptying and cleaning needs depend on the cistern, its material, and how it is used, so follow guidance from a qualified professional or the tank manufacturer where known. Keep a note of repairs and changes so future users understand the system’s limits.
Common Mistakes
- Assuming clear water is clean. Appearance cannot rule out harmful contamination. Treat water as non-potable unless its suitability has been established for the intended use.
- Entering the tank. A cistern is an enclosed space, not a safe place to climb into for routine cleaning. Use an outside inspection or professional service instead.
- Ignoring the tank’s history. An old cistern may have held something other than rainwater. Unknown use should lead to caution, not guesswork.
- Using unsuitable cleaning products. A chemical that removes dirt may damage a liner or leave residues. Check material compatibility and intended use before cleaning.
- Leaving the opening uncovered. An unsecured lid can allow falls, debris, or animals into the tank. Secure the cover and restrict access during work.
- Forgetting overflow. A cistern that fills without a safe overflow route can cause water damage or pooling. Plan where excess water will go before connecting an inlet.
- Connecting it to clean plumbing casually. Cross-connections can allow non-potable water to contaminate a drinking-water system. Keep systems separate and have any proposed plumbing connection reviewed professionally.
Tips
- Photograph the tank, fittings, and surrounding area before making changes. This helps you compare conditions later and explain the setup to a professional.
- Label any reused-water outlet clearly as non-potable if that applies, and make the label easy to see where someone might use the water.
- Prefer a simple setup with accessible screens, visible joints, and a clearly directed overflow. Components that are easy to inspect are easier to maintain.
- Keep stored water covered and limit access by insects and animals. Do not rely on a screen alone if the opening itself is not secure.
- Plan for periods when the cistern is empty. A pump should not be allowed to run dry unless its design permits it; check its instructions or ask a qualified installer.
- For a decorative conversion, consider whether the structure can retain water and whether standing water can be managed safely. If not, use it as a dry landscape feature instead.
Troubleshooting
The cistern leaks after filling. Stop adding water and identify whether the leak is at a fitting, visible crack, or base. Do not seal a structural crack with an unverified product. Emptying or repair may require specialist equipment, particularly for a buried cistern.
Water is not reaching the tank. Check for a blocked screen, disconnected inlet, or a route that sends runoff elsewhere. Work from accessible points only. Do not climb onto an unsafe roof or remove a pipe that may connect to another system.
The tank fills but overflows in the wrong place. Stop collection if you can do so safely, then redirect or repair the overflow so water cannot undermine foundations, erode soil, or enter an unsuitable drain. Get local advice if the correct discharge point is unclear.
Water smells or looks unusual. Do not use it. Keep people and animals away, avoid adding chemicals to mask the problem, and seek professional help to identify the source. If contamination is suspected, a qualified assessor can advise whether testing or disposal is needed.
The cover does not fit or the structure shifts. Keep the area closed off and do not load, fill, or use the cistern until it has been inspected. A poor fit may indicate damage, movement, or a cover that is not designed for the opening.
Frequently Asked Questions
Can I use an old cistern for drinking water?
Not without confirming its history, condition, and water quality, and ensuring the system meets applicable requirements. Cleaning by itself does not establish that water is potable. Ask the relevant local authority and a qualified water professional before considering drinking use.
Can I use cistern water on vegetables?
Do not assume that rainwater from an old tank is suitable for edible plants. Contamination can come from the tank, roof, plumbing, or surrounding area. Check official local guidance and seek qualified advice before using it on food crops.
Is it safe to climb inside to clean it?
No. Do not enter a cistern for inspection or cleaning. The opening, air conditions, and difficulty of rescue can make entry dangerous. Arrange professional cleaning or inspection when work cannot be done safely from outside.
What if I do not know what the cistern held?
Do not disturb suspicious residue or connect the tank to a water system. Use visible clues and available property records, then ask a qualified professional to assess it. Until its history and condition are understood, do not use its water for people, animals, or edible crops.
Can a cistern be reused as a pond?
Possibly, if the structure is sound and the conversion can be managed safely. Check for leaks, secure access, and consider how standing water and overflow will be handled. Do not add animals or aquatic plants until you know the water and lining are suitable for them.
What is the simplest reuse if the tank is damaged?
Do not fill or rely on a damaged cistern. After a qualified assessment, it may be possible to keep it as a dry garden feature or remove it safely. A professional can advise whether the structure can remain in place without creating a hazard.