Is Your Solar Geyser Producing Enough Hot Water?

Common Issues That Affect Solar Geysers and How To Fix Them

A good quality solar geyser will give you between 15 to 20 years of use.

But just like a car that goes through everyday use, your geyser will experience some wear and tear. And just like a car, your geyser needs an occasional tune up to keep it in good shape.

In this post, we’ll cover the most common reasons a solar geyser might not produce enough hot water and how you can fix it.

We’ll also give you a basic guide on how to maintain your geyser to keep it working in peak condition.

Why your solar geyser is not producing enough hot water

In winter and on cloudy days, a solar water heater doesn’t produce as much hot water if running on solar alone. You can read all about why in my beginner’s guide to solar geysers.

But if your solar geyser is not producing enough hot water even on clear sunny days, then either the sizing, shading or equipment is at fault. Let’s look at each of these.

1. Is it the correct size?

Is your geyser the right size for your needs? It might just be that there are more heads in your household than the geyser can handle.

This is one instance where size does matter. Depending on your consumption habits, you need a 300l size system for a family of between 4-6 people.

2. Is it getting enough sun?

Assuming your system is big enough, the next thing to check is whether it’s placed where it can get the maximum amount of sunlight.

Site and install your geyser correctly, making sure there are no overgrown trees or buildings that will throw it in shade.

Shading reduces the efficiency of your geyser. Installing it properly increases its efficiency.

You can increase the efficiency by installing the geyser to:

  1. Face the direction (true north) in which it captures the maximum hours of peak sunlight. North West or North East can work as well, although this reduces the sunlight your geyser receives.
  2. Tilted at an angle (minimum of 20°) at which it captures the most hours of sunlight.

3. Basic equipment checks you should do

Check on the system equipment to make sure everything is at it should be.

Check for leaks

Make sure there are no leaks or cracks in the piping, the collector, the storage tank or anywhere else.

Is there water anywhere in the system where it shouldn’t be?

Check the parts or system components

If your system has components like a backup element, for example, check that the thermostat is not set too low.

Check your pumps, sensors, and controllers should also to make sure they’re in working order.

While you’re at it, check for corrosion or loose fittings/supports.

Always refer to your owner’s manual before you do any sort of maintenance on your geyser.

Check for dirt

Dirt or sediment, either on the collector (tubes/flat panel) or in the storage tank, will reduce the amount of hot water you’re going to get from your system.

Below, we’ll look at when and how you should clean your solar geyser.

How to clean your solar geyser

Dirt will reduce the efficiency of a solar water heater. This can happen in two ways:

  1. A layer of dust settles on the tubes or panels during the year or from construction work nearby.
  2. Sediment forming in the storage tank.

Cleaning a solar geyser of dust or sediment is relatively simple by following the steps outlined below.

Cleaning the collector

In most cases, good old-fashioned rain will wash away the dirt.

But in a dry year, you might need to take matters into your own hands.

If there hasn’t been enough rain, a hosing down of the tubes or panels using light to medium pressure is enough.

Do this in the early morning or late evening.

Alternatively, wipe them down with a wet or dry rag.

Cleaning the insides

Water has minerals and treatment chemicals in it.

Heating water causes chemical reactions to occur. This leads to the buildup of sediment or scale that reduces a solar or electric geyser’s ability to heat and circulate water.

Scale will collect in the piping and the tank of your water heater. You can clean these out with vinegar by following these steps.

  1. Refer to the manual for your solar geyser before you do anything.
  2. Power down the geyser.
  3. Turn off the cold-water input.
  4. Drain out the hot water.
  5. Carefully remove each tube and shake out each tube to remove the hard scale.
  6. Flush the tubes with vinegar to remove the remaining scale.

Alternatively, you can circulate the vinegar through the system if you don’t want to remove the tubes or if your solar geyser is mounted where it’s difficult to reach.


To some up. To ensure your solar geyser produces enough hot water, make sure to:

  • Correctly size your system.
  • Correctly site your system.
  • Carry out regular maintenance on your system.

How good are your solar smarts? Take the Solar 101 Quiz and find out in 5 minutes!

How often should I clean my solar geyser?

You should look to do this at least once a year or two at most.

What chemicals or special equipment do I need?

You don’t need to go out and buy any special product. Water and soap will do for the outside. Vinegar for the inside.

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