Care home sentinel temperatures, dead legs and an unprotected sprayer fill point
A 30-bed residential care home has a 500 L unvented calorifier stored at 62 °C with a blending valve at the calorifier outlet set to 45 °C. Monthly monitoring shows the sentinel hot outlet in room 12, the least used room, at 41 °C after one minute; the cold supply to the same room at 23 °C after two minutes in July; and the calorifier return at 48 °C. Two dead legs remain from removed washbasins, each about 1.2 m of capped 15 mm pipe. In the sluice room a cleaner's tap with a 1 m hose is used to fill a bucket with detergent and occasionally to fill a weed-killer sprayer; there is no backflow device. The unvented cylinder was installed 18 months ago and the last Legionella risk assessment is dated four years ago.
1. Interpret the monitoring results against current Legionella guidance and set out the actions in priority order with realistic timescales.
Read the worked answer
Compare each result with HSG274 guidance, which applies to care homes under the L8 Approved Code of Practice.
- Sentinel hot outlet at 41 °C after one minute: the target is 55 °C after one minute, so this is a failure, and it is at the least-used outlet where stagnation is expected.
- Cold supply at 23 °C after two minutes in July: the target is below 20 °C, so this is also a failure. Warm incoming mains in summer may explain part of it, but it still needs investigating.
- Calorifier return at 48 °C against a target of 50 °C: marginal but below specification.
Root cause: the blending valve is at the calorifier outlet and set to 45 °C, so the whole distribution runs at 45 °C. That makes 55 °C at outlets impossible and 50 °C on the return unachievable. The design should store at 60 °C, distribute at 55 °C or above, and blend at the point of use, with thermostatic mixing valves on baths, basins and showers.
Actions in order:
- Record the results and inform the responsible person the same day.
- Review the risk assessment, which is four years old and overdue, and update the written scheme.
- Remove the two dead legs, cutting back to the main rather than leaving them on a list.
- Reset the calorifier to 60 °C, move blending to outlets, flush all outlets and retest sentinels.
- Take Legionella samples from a sentinel and a representative outlet before and after remediation, and clean and chlorinate shower heads and hoses.
- Increase sentinel monitoring frequency until three consecutive satisfactory results are obtained.
2. Assess the backflow risk of the two sluice room uses and specify the protection required, explaining why a single device type will not cover both.
Read the worked answer
Both connections need protection, but at different fluid categories.
Cleaner's tap with a 1 m hose. A hose union tap is a recognised backflow risk because the hose can be left submerged in a bucket of detergent, which is fluid category 3. A hose union tap on the mains should have at least a double check valve, either a tap with an integral check valve or a type HD device. If a hose can be connected and left in a bucket, category 3 protection is the minimum.
Weed-killer sprayer. Filling a pesticide sprayer from a tap, even occasionally, creates a category 5 risk, the highest, because a toxic substance can be drawn back into the mains. Nothing less than an air gap (type AA or AB) or a reduced pressure zone valve (type BA) is acceptable. A double check valve cannot be used for category 5.
Practical specification:
- Remove the hose from the cleaner's tap, or fit a hose union tap with an integral double check valve and display a notice.
- Install a dedicated outside fill point with a type BA RPZ for the sprayer, located above ground, drainable and tested annually. Alternatively use an air gap into a break tank and draw from that tank, which avoids the RPZ maintenance burden.
- Label all fill points with the fluid category and the equipment served.
- Record the changes in the water safety plan and add the RPZ to the maintenance schedule.
Do not rely on a temporary hose and a verbal instruction; treat the sprayer as category 5 until physical protection is installed.