bar mixer shower temperature problems

Many households experience issues with fluctuating water temperatures in bar mixer showers, which can be both uncomfortable and unsafe. This article explores a common problem related to inconsistent water temperatures in showers and offers potential solutions, focusing on a case involving a Potterton Performa 28 combi boiler and a Gainsborough mixer shower.

Problem: Inconsistent Shower Water Temperature

The main issue described involves water temperature in the shower fluctuating from hot to cold and then back to hot. This inconsistency occurs despite replacing a previous thermostatic shower unit, suggesting that the problem may not be with the shower hardware itself.

Potential Causes and Solutions

  1. Other Water Demands: Initially, it is essential to determine whether the temperature fluctuation correlates with other water demands in the household, such as the toilet refilling or the kitchen tap being used. However, in this case, the problem persists independently of other water demands.
  2. Water Hardness: Hard water can cause limescale buildup, which might affect the shower’s performance. If the water in the area is hard, as mentioned, this could be contributing to the issue.
  3. Thermostatic Unit Malfunction: While the shower is not currently thermostatic, it’s possible that previous issues might have been due to limescale damage in the thermostatic unit. In hard water areas, limescale can impede the smooth operation of shower controls.
  4. Boiler Functionality: Since the boiler has been checked and is functioning correctly, the issue is likely not related to the boiler’s ability to deliver hot water.
  5. Testing with Bath Hot Tap: An essential test is to run the bath hot tap alone to check for temperature fluctuations. If the bath water temperature remains constant while the shower temperature fluctuates, this suggests a problem specific to the shower system.

Investigating Shower-Specific Problems

  1. Mixer Valve Issues: In a non-thermostatic mixer shower, the blending of hot and cold water is manual. If there are issues with the mixer valve, this could cause temperature inconsistencies.
  2. Pressure Imbalances: A pressure reducing valve on the cold water supply to the shower might help if there is a significant pressure difference between the hot and cold supplies.
  3. Limescale Buildup: Cleaning or replacing parts affected by limescale, especially if the water is hard, could improve the situation.

Seeking Professional Assistance

  1. Consult a Plumber: For persistent issues, consult a professional plumber. They can assess the shower system and provide solutions specific to the setup.
  2. Professional Cleaning or Replacement: If limescale is a suspected problem, professional cleaning or part replacement might be necessary.
  3. Exploring Different Shower Systems: If the problem continues, considering a different type of shower system that might be more compatible with the household’s plumbing could be an option.


Fluctuating shower temperatures in a system like the Potterton Performa 28 combi boiler and Gainsborough mixer can be frustrating. Investigating the cause, whether it’s related to water hardness, pressure imbalances, or mixer valve issues, is crucial. Professional assessment and potential part replacement or system alteration can provide a solution. Regular maintenance, especially in areas with hard water, is also essential to prevent similar issues.

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *