Project Overview
| Location | Wimbledon, south-west London |
|---|---|
| Call-out | Emergency — no hot water |
| System | Vaillant ecoTEC Plus with unvented cylinder (S-plan) |
| Fault found | Failed hot water zone valve |
| Work completed | EPH 2-port hot water and heating zone valves replaced |
The Challenge
A household in Wimbledon had lost domestic hot water and needed a Gas Safe emergency plumber the same day. On an S-plan heating system the hot water circuit is opened by a 2-port motorised zone valve. When that valve sticks or the actuator fails, the boiler can still fire for central heating while the cylinder is starved of heat — a classic “heating works, no hot water” fault.
The job was to diagnose the no-hot-water fault quickly, restore hot water on the first visit, and leave the heating controls in a reliable condition.
The Solution: EPH Zone Valve Replacement
On arrival we tested both motorised zone valves. The hot water zone valve was not opening correctly, which matched the loss of hot water. Rather than change only the failed actuator, we replaced the complete 2-port valves on both the hot water and heating circuits with new EPH motorised zone valves.
Replacing the pair is the reliable repair on an S-plan system of this age: both valves work in the same conditions, and changing one while leaving its twin in place often leads to a second emergency call-out when the heating valve fails next. After fitting, both EPH valves were confirmed opening and closing correctly and hot water was restored before we left site.
Why EPH 2-Port Zone Valves
EPH motorised zone valves are a Gas Safe engineer’s standard replacement on UK S-plan and Y-plan systems. For this Wimbledon no-hot-water repair they gave a clean, like-for-like upgrade:
- Positive hot-water control: A working 2-port valve opens the cylinder circuit on demand so the Vaillant ecoTEC Plus can heat stored water instead of only the radiators.
- Matched heating circuit: Fitting a second EPH valve on the heating pipework keeps both zones on the same actuator type, wiring and spare parts.
- Manual override: The lever on the valve body lets the engineer prove flow during commissioning and gives a temporary open position if a future actuator fault occurs.
- Quiet, compact actuators: The new heads sit neatly on existing copper pipework alongside the Grundfos UPS3 circulating pump already serving the system.
The Repair Process
- Arrival and diagnosis: We isolated the system, checked programmer and thermostat demand, then tested the hot water and heating zone valves. The hot water valve was not operating as it should.
- Valve replacement: Both 2-port valve bodies and actuators were replaced with EPH units, wired back into the existing S-plan controls, and the pipework joints were checked for leaks.
- Commissioning: Hot water and heating zones were run independently. Both new valves opened and closed correctly and hot water returned to the cylinder.
- Advice on site: We flagged follow-up work that would improve long-term reliability: a proper bracket for the expansion vessel, a full strip-down boiler service, and a check-over of the unvented cylinder.
The Results
Hot water was restored on the same emergency visit. The Wimbledon home now has new EPH 2-port valves on both the hot water and heating circuits, so the Vaillant ecoTEC Plus can serve the unvented cylinder and the radiators independently again. No second attendance was needed to get the family back to hot water.
Recommended Follow-Up
While on site we noted three items that were not part of the emergency repair, but will keep this system reliable:
- Expansion vessel support: The Zilmet vessel is currently carried by the pipework only. It should be fitted with a proper wall bracket so the cylinder connections are not taking the weight.
- Boiler service: A full strip-down service of the Vaillant ecoTEC Plus is the next planned maintenance visit — the right time to clean, inspect and recertify the appliance.
- Unvented cylinder check: A periodic inspection of the unvented cylinder, expansion vessels, temperature/pressure relief and incoming stopcock keeps the stored-hot-water side compliant and safe.
