Frequently Asked Questions
Everything you need to know about water sampling, testing, and results
Sampling & Collection
Can I take the water samples myself?
You can take the samples yourself. Our kits are designed for safe and accurate self-sampling. Clear instructions are included with every kit. When bottles are handled correctly and returned promptly, self-collected samples provide reliable laboratory results.
How many samples do I need?
The number of samples depends on: building size, number of outlets, presence of tanks, system complexity, and risk assessment findings. Most systems require at least two representative samples, with additional samples from tanks and sentinel outlets. Use our Sample Calculator for guidance.
How do I take a water sample correctly?
Wash and dry your hands, avoid touching the inside of the bottle or lid, fill to the marked line, seal immediately and return the sample the same day. Following the instructions carefully helps ensure accurate results.
Do I need to disinfect the tap before sampling?
No — do not disinfect chemically clean the outlet unless specifically instructed. The aim is to test the water supplied at the outlet, not alter the conditions.
How should samples be stored before posting?
Keep samples cool, out of direct sunlight, and away from heat sources. Samples should be returned to the lab on the same day they are taken.
Where do I drop off my samples?
Seal the box and hand it in at any Royal Mail Post Office counter.
With thousands of Post Office locations across the UK, drop-off is quick and convenient.
Legionella & TVC Testing
What is Legionella?
Legionella is a naturally occurring bacteria that can grow in water systems such as tanks, pipework, showers and outlets. Inhaling contaminated water droplets can cause Legionnaires' disease, a serious type of pneumonia. Regular monitoring and good water management help reduce the risk.
What is TVC (Total Viable Count)?
TVC measures the overall level of general bacteria in water. It does not identify specific harmful organisms but indicates how active bacterial growth is within the system. Elevated TVC levels can highlight stagnation or poor water turnover before other issues develop.
Do I need both Legionella and TVC testing?
Legionella and TVC measure different aspects of water quality. Legionella testing looks for a specific pathogen, while TVC indicates overall bacterial activity. Many premises choose both tests for a broader picture of system condition, but the appropriate combination depends on your risk assessment and monitoring plan.
How often should Legionella samples be taken?
Sampling frequency should follow your Legionella Risk Assessment. In many premises, sampling is carried out every six months, with more frequent testing in higher-risk environments such as care homes, healthcare settings, hotels or buildings with stored water.
How often should TVC samples be taken?
TVC is commonly taken alongside Legionella sampling. Typical practice includes: 6-monthly sampling from potable water tanks, periodic checks on outlets, additional testing where stagnation or water quality concerns exist.
Should water tanks be sampled?
In most systems, water tanks are sampled as part of routine monitoring because water is stored for longer periods, increasing the likelihood of stagnation and bacterial growth.
Many monitoring programmes include
taking both Legionella and TVC samples from potable tanks as part of routine monitoring.
Results & Actions
What do my results mean?
Your report will show the laboratory CFU results for each sample and include general guidance notes. These results help inform whether further investigation or action may be appropriate.
For detailed guidance on interpreting Legionella and TVC results, including action levels and recommended next steps, see our Water Sample Collection & Results Guide.
How long do results take?
Results are typically provided within 10–14 days from the day samples are posted. Posting samples the same day helps avoid delays.
What does 'cfu' mean?
CFU stands for Colony Forming Units. It is the measurement used to estimate the number of bacteria present in a water sample. Higher CFU counts indicate greater bacterial activity.
What Legionella level is considered satisfactory?
Results where Legionella is not detected are generally considered satisfactory. Low counts may only require monitoring, while higher counts may require investigation or remedial action in line with your risk assessment.
What happens if my Legionella result is positive?
If Legionella is detected: review temperatures and control measures, flush infrequently used outlets, inspect tanks and pipework, consider cleaning or disinfection, and repeat sampling. Higher results may require specialist advice and urgent remedial action.
What happens if my TVC result is high?
Elevated TVC levels suggest general bacterial growth. This may be linked to stagnation, poor turnover or temperature issues. Flushing, cleaning and reviewing management practices are commonly recommended.
Does water testing replace a Legionella Risk Assessment?
Water testing provides a snapshot of conditions at the time of sampling, while a risk assessment evaluates the entire system and management controls. Testing should form part of a wider water safety programme, alongside a suitable risk assessment.
If you require a Legionella Risk Assessment please complete our form. We will arrange for our specialist Risk Assessment partners to contact you and provide a free no obligation quotation.
If you’re responsible for a building and unsure where to start, routine water testing offers a practical way to gain clarity on your system.
Compliance & Responsibility
Are these kits suitable for homes and landlords?
Our kits are suitable for domestic properties, landlords, small businesses and commercial premises. If you are unsure what you need, contact us and we can guide you.
Who is responsible for water testing?
Under health and safety regulations, the building owner or manager is responsible for ensuring water safety. This includes conducting risk assessments and arranging appropriate testing. You may delegate tasks to a competent person or water management consultant, but ultimate responsibility remains with the organization. Ensure your team understands their roles and responsibilities.
What regulations apply to water testing?
In the UK, duties relating to Legionella control typically arise under the Health and Safety at Work etc. Act 1974 and supporting guidance such as the Approved Code of Practice L8 (ACOP L8) and HSG274. These documents set out responsibilities for managing water systems and controlling risk. Always refer to current official guidance or seek competent advice to ensure compliance.
How should I keep records of results?
Maintain detailed records including: sample dates and locations, results received, any positive findings, corrective actions taken, and follow-up testing.
Many organisations retain records for several years in line with current guidance.
Digital records are acceptable but ensure they're backed up. Good record-keeping demonstrates due diligence and helps identify trends in your water system.
Do I need to report positive results to authorities?
Reporting requirements vary depending on building type and local regulations. A positive water sample result does not automatically require notification. However, confirmed cases of Legionnaires’ disease or outbreaks may be reportable to the Health and Safety Executive (HSE). If unsure, seek competent advice.
What can affect results?
Why is same-day posting important?
Delays or heat exposure can affect sample condition and reduce reliability. Posting on the same day helps ensure results accurately reflect the water at the time of sampling.
What if I think my sample was contaminated?
Do not send the sample. Use a spare bottle if available or contact us for advice. Contaminated samples may produce inaccurate results.
Why do I keep getting positive results?
Persistent positive results suggest systemic issues in your water system. Common causes include: inadequate water temperature control, stagnant water in dead legs or unused outlets, biofilm formation, poor maintenance, or inadequate chlorination. Work with a water management consultant to identify the root cause and implement comprehensive corrective measures. This may require system modifications or upgrades.
What is a dead leg and why is it a problem?
A dead leg is a section of pipework that has little or no water flow, often created by redundant connections or poorly designed systems. Water stagnates in dead legs, allowing bacteria to grow and biofilm to form. Dead legs should be removed or flushed regularly. Identify and eliminate dead legs during your risk assessment to improve water quality and reduce testing issues.
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