There are two main types of shower enclosure operation devices available on the common mixer shower - manual mixers and thermostatic mixers. Both mixers provide the same end result of allowing water to flow from the shower head when you want it to and how you want it to, but different users have different operation preferences.
Manual Mixers - The classic method of shower mixing used by most showers available on the market is the manual mixer. The user is able to manually adjust the temperature of the water by turning the mixer in a corresponding direction for more hot or cold water. By adjusting the direction of the mixer, the user is able to manually achieve the shower temperature that they desire.
As the manual mixer works from the mains feed of the cold water supply and the mains feed of the hot water supply, the pressure is typically higher than most electrical shower systems. However, manual mixers are unable to balance the pressure of both water feeds so a pressure equalising valve is required. Without a pressure equalising valve, the user may find that hot and cold water pressure can drop suddenly when called from another outlet.
Manual mixers are generally cheaper to purchase than thermostatic mixers, but they do not offer the safety benefits or operation management.
Thermostatic Valve Mixers - A thermostatic valve utilises a temperature sensitive cartridge (often made from ceramic) mounted inside the main housing of the valve. A thermostatic valve allows the user to set a constant temperature for the water output, with pressure often set by a simple level valve. By working to maintain a constant temperature, using a thermostatic valve eliminates unexpected fluctuations of hot or cold water when called from different outlet. Instead, the valve will automatically compensate either supply in order to maintain the user set temperature.
Due to this built in "safety feature" thermostatic valves have gradually become the first choice for many home users, providing the safest form of showering for any age group. Most thermostatic valves are factory set to manage incoming water at a maximum "safe" temperature (usually around 38) but this can be manually adjusted easily by the user depending on preference.
Thermostatic valves also work well in most systems but are not advisable for systems with consistent imbalances in pressure. If this is the case with your water system, be sure to check ensure that your water flow to the cabin can be kept at a constant through the use of pressure equalising valves or isolating valves. If such precautions are not taken, it is common for a thermostatic valve to malfunction and not operate as expected. Long term usage in poor circumstances could cause permanent damage to the internal workings of the thermostatic core, which could lead to needing a replacement. Replacing a thermostatic valve can one of the more expensive elements of shower enclosure maintenance so take extra precaution.