Will a Gas Geyser Work With My Mixer Taps?
It depends entirely on the unit. The Paloma 20L and Rinnai 20L are built for mixers and hold temperature while you adjust the tap. The Dewhot 16L generally copes. The Cadac and older diaphragm-style units often struggle, because throttling the flow at the mixer can drop it below the level the geyser needs to stay lit.
Why do mixers confuse some gas geysers?
A gas geyser only lights when it senses water flowing through it. A mixer tap works by blending cold into the hot, which means less water is being pulled through the geyser than the tap is delivering to you.
Get the balance wrong and the flow through the unit falls under its ignition threshold. The burner cuts out, cold water arrives at the shower, you turn the hot up, the flow rises, the burner relights and a slug of hot water hits you. That is the hot-cold-hot dance homeowners describe when they phone us, and it is almost never a broken geyser — it is the wrong unit on a mixer, or a plumbing layout starving it.
Modulating units solve this properly. Instead of running full or nothing, they vary the burner to hold your set temperature across a range of flows, so mixing down at the tap does not upset them.
Which units handle mixer taps best?
In order: Paloma and Rinnai first, Dewhot next, Cadac last. That is not a ranking of quality — each unit has a home it suits — it is a ranking of how they behave when you mix flow down at the tap.
- Paloma 20L and Rinnai 20L. Constant-temperature, modulating units made for mixer taps and multiple bathrooms. Set the temperature once and the unit holds it while you adjust the tap. Both need a weatherproof plug point.
- Dewhot 16L Constant Temperature. Generally fine on mixers in a standard home. How well it behaves depends on your plumbing — pipe size, length of run and how many outlets are used at once.
- Cadac 16L Ecoflow. May work depending on flow conditions, and its low-flow start helps, but it is not our first choice where mixers matter. It earns its place in flats and granny flats.
What if my mixer shower goes hot and cold?
Do not assume the geyser is finished. Nine times out of ten it is a flow threshold problem or a plumbing layout issue, and sometimes the fix is a setup change rather than a new unit.
Our fault diagnosis visit checks what the unit is actually seeing: the flow sensor and spinner, the inlet filter, the gas supply and regulator, the set temperature, and how the pipework is feeding the bathroom. A partially blocked inlet filter alone can push a perfectly healthy unit under its threshold.
If the unit really is the wrong one for a mixer-heavy house, you get told that plainly and given the options — including what it costs to move up to a modulating unit through our replacement service. We do not condemn geysers to sell new ones; the workshop rule here is fix first, replace only when it makes sense.
Does pipe size and layout matter?
More than most people expect. The geyser can only work with the water that reaches it, and the pipe feeding it decides how much that is.
- 16mm vs 20mm feeds. A 20mm feed carries more flow to the unit and copes far better when two outlets run together. Older homes around George are often on 16mm throughout.
- Length of run. A long run from the geyser to the bathroom means a wait for hot water and more heat lost on the way, which tempts people to open the hot side further and unsettle the balance.
- Simultaneous use. Two showers and a kitchen tap at once needs a 20 litre unit. Asking a 16 litre unit to do it will always disappoint somebody.
- Where the unit sits. Mounting closer to the main bathroom usually beats mounting where the pipe happens to be convenient.
If you are still choosing, the buying guide compares all five models, and gas geyser installations covers what a full fit involves.
Mixer Taps and Gas Geysers — Common Questions
Sometimes, depending on your flow conditions — but it is not the reason to buy one. The Cadac 16L Ecoflow is built to light on weak flow, which helps, yet a mixer that is barely cracked open can still drop the flow under what the unit needs and it will shut down. If your bathrooms are all on mixers and you want a hot shower you can set and forget, the Paloma or Rinnai is the right unit. The Cadac remains an excellent choice for flats, granny flats and low-pressure situations.
Hot then cold in the shower? Let's find out why.
Describe what your shower does and which taps you have. we will tell you whether it is a setup fix, a plumbing fix or the wrong unit for the house.