Low water pressure and no hot water can appear to be part of the same plumbing problem.
However, these symptoms can come from completely separate faults within the property.
A recent investigation involved a solar hot water system that was not providing enough hot water, along with reduced water pressure throughout the home.
The solar heating side of the system was operating correctly. The hot water fault was traced back to the thermostat within the solar water heater, while the pressure issue was linked to the pressure control valve on the incoming water supply.
Why Solar Hot Water Can Become Unreliable in Winter
Solar hot water systems use energy collected from the sun to heat water stored within the system.
During warmer and sunnier conditions, the solar contribution may provide most or all of the hot water required by the household.
Winter conditions can be different.
Shorter days, lower sun angles, cloud cover and colder incoming water temperatures can reduce the amount of useful solar energy collected throughout the day.
This does not necessarily mean the solar panels, circulation system or collector loop have failed. It may simply mean the available solar gain is not enough to meet the household’s hot water demand.
The Solar Side Was Working Correctly
When diagnosing a solar hot water problem, it is important to determine which part of the system is actually responsible.
The solar collection and heating side of this system was checked and found to be operating correctly.
This ruled out a broader failure of the solar heating process and allowed the investigation to focus on the backup heating system.
The fault was ultimately traced to the thermostat within the solar water heater.
What Does the Solar Hot Water Booster Do?
The booster provides additional heating when the solar contribution is not sufficient to bring the stored water up to the required temperature.
This becomes particularly important during winter, extended wet weather or periods of heavy household hot water use.
Without effective boosting, the system may still collect some heat from the sun but fail to produce enough hot water for showers, washing and normal household use.
Homeowners should understand when the booster needs to be switched on and how long it may need to operate. Leaving it permanently off during low-solar conditions can result in consistently lukewarm or insufficient hot water.
At the same time, the booster should not be used to conceal an underlying fault. If the system remains cold even when the booster is operating, the thermostat, heating element, electrical supply or another component may require investigation.
Why the Thermostat Matters
The thermostat controls the temperature of the electrically boosted water and regulates when the heating element operates.
When the thermostat is faulty, the booster may not heat the water correctly even though the solar side of the system continues to operate.
This can create confusing symptoms because the system may produce some warmth during sunny conditions but fail to maintain a reliable hot water supply.
Correct diagnosis prevents functional solar components from being replaced unnecessarily and ensures attention is directed to the actual fault.
Why Was the Water Pressure Low?
The low water pressure was a separate issue from the hot water fault.
The incoming water supply passes through pressure control equipment before being distributed through the property.
A pressure control valve that is restricted, failing or no longer operating correctly can reduce the available pressure throughout the home.
Depending on the installation, low pressure may affect:
- Hot and cold taps throughout the property
- Showers
- Toilet cistern filling
- Washing machines and dishwashers
- Garden taps
- The performance of the hot water system
When both hot and cold water pressure are weak across multiple fixtures, the incoming supply, meter valve, pressure control valve or main water line should be considered.
Low Hot Water Pressure Versus Low Whole-House Pressure
Identifying where the pressure problem occurs can help narrow down the likely cause.
Low pressure on hot and cold water
When pressure is reduced on both sides throughout the property, the fault may be associated with the incoming water supply, pressure control valve, partially closed meter valve or a restriction within the main pipework.
Low pressure only on the hot water side
When the cold water pressure remains normal, the restriction may be associated with the hot water system, tempering valve, isolation valve or hot water pipework.
Low pressure at one fixture
When only one tap or shower is affected, the cause may be a blocked aerator, restricted shower head, faulty mixer cartridge or partially closed isolation valve.
Two Symptoms Require Two Proper Diagnoses
It would have been easy to assume the low pressure was preventing the solar hot water system from operating correctly, or that the solar system was responsible for every symptom.
Instead, the investigation identified two distinct issues:
- A thermostat fault affecting the boosted heating of the solar hot water system
- A pressure control valve contributing to reduced water pressure entering the property
Separating the symptoms prevents unnecessary replacement work and allows each part of the plumbing system to be addressed correctly.
When Should a Solar Hot Water System Be Inspected?
A solar hot water system should be inspected when:
- The water remains cold when the booster is switched on
- Hot water becomes unreliable during winter
- The system produces only lukewarm water
- The booster trips the electrical circuit
- Water is continually discharging from a valve
- The system makes unusual noises
- Hot water pressure has reduced
- The system has not been serviced for an extended period
The correct repair depends on whether the problem is associated with the solar collectors, circulation, thermostat, heating element, valves, electrical supply or the surrounding plumbing.
Solar Hot Water and Water Pressure Services
RJT Plumbing & Gas diagnoses solar hot water faults, low water pressure, pressure control valve issues and general hot water problems throughout North Lakes and surrounding Moreton Bay suburbs.
A proper investigation can determine whether the fault is within the solar heating system, electrical booster, incoming water supply or another part of the property’s plumbing.
For assistance with low water pressure or an unreliable solar hot water system, contact RJT Plumbing & Gas.
Frequently Asked Questions
Why does my solar hot water system stop producing enough hot water in winter?
Shorter days, lower sun angles, cloud cover and colder incoming water can reduce the amount of heat collected by a solar hot water system during winter. The solar side may still be operating correctly, but the electrical booster may be needed to bring the stored water up to the required temperature.
What does the booster switch do on a solar hot water system?
The booster switch activates the system's backup heating when solar energy alone is not producing enough hot water. It is commonly required during winter, extended cloudy weather or periods of higher household hot water use.
Should the solar hot water booster be left on all the time?
The correct booster use depends on the system, weather conditions and household demand. Some homes may only need boosting during colder or overcast periods. If the water remains cold while the booster is switched on, the thermostat, heating element, electrical supply or another component may require inspection.
What happens when a solar hot water thermostat fails?
A faulty thermostat can prevent the booster heating element from operating correctly or regulating the stored water temperature. The solar collectors may still produce some heat, but the household may experience lukewarm water, inconsistent hot water or no effective boosted heating.
Can the solar collectors work correctly while the hot water booster has a fault?
Yes. The solar collection system and the backup heating system perform different functions. The collectors may be operating correctly while a thermostat, heating element, electrical supply or booster control fault prevents the system from providing reliable hot water.
Can a pressure control valve cause low water pressure throughout a house?
Yes. A restricted, faulty or incorrectly operating pressure control valve on the incoming water supply can reduce water pressure across multiple taps, showers and appliances throughout the property.
How can I tell whether low pressure is affecting the whole property or only the hot water?
Test several hot and cold taps throughout the property. If both hot and cold pressure are low, the incoming water supply, pressure control valve, meter valve or main pipework may be involved. If only the hot water pressure is low, the restriction may be within the hot water system, tempering valve or hot water pipework.
Are low water pressure and no hot water always caused by the same fault?
No. Low water pressure and unreliable hot water can occur at the same time but have separate causes. Each symptom should be diagnosed independently so that the pressure system, solar collectors, booster heating and hot water components can be checked properly.
When should a solar hot water system be inspected?
A solar hot water system should be inspected when the water remains cold with the booster switched on, hot water becomes unreliable, the system produces only lukewarm water, pressure drops, valves continually discharge or the system begins making unusual noises.
Does RJT Plumbing and Gas diagnose solar hot water and low-pressure problems?
Yes. RJT Plumbing & Gas diagnoses solar hot water faults, booster and thermostat issues, low water pressure, pressure control valve problems and general hot water faults throughout North Lakes and surrounding Moreton Bay suburbs.
