Hi everyone

We recently bought a house that has all gas geysers / water heaters and there is an inconsistency with the hot water flow. 

𝗧𝗵𝗲 𝘀𝘆𝘀𝘁𝗲𝗺

Medium size gas heater, set to 65 degree celcius

two x 19kg gas bottels: Switching between the two as the pressure decreases. 

Copper pipes to the showers, baths and basins. 

Mixer taps

𝗧𝗵𝗲 𝗽𝗿𝗼𝗯𝗹𝗲𝗺

I will open the mixer taps until there is hot water, then slightly adjust the tap to the desired water temperature.

Thereafter, the water will get very hot as if the cold water stops flowing.

It will be like this for about two minutes then return to the initial mixed temperature. 

After about 5 minutes, the water will become cold and this lasts about another 3 - 5 minutes. 

I will close the tap completely, then open it again and only thereafter the hot water returns but only to start the entire  cycle again.

This happens every time regardless if I replace the gas bottles, replace the batteries or adjust the temperature on the geyser. 

I need to add, I have zero experience with these types of systems. 

Can any of you gas-system-brainiacs steer me in the right direction?

 

Speculating here, but that may be your temperature regulation valve/circuit of your gas geyser itself that may be faulty, i.e. the temp probe or sensors could be defective or an internal mixing/regulating valve.
Alternatively, is it possible that your mixer taps may be interfering with the water temp regulation of the geyser where changing water pressure between cold and hot created by the mixer tap possibly affects the geysers internal temperature regulation?
Maybe check with the Geyser manufacturer/supplier what the possible cause could be.

 

A minimum water flow is necessary to keep the geyser on. Maybe the water is so hot that hot water flow is too low in the mixer tap to keep gas burning.

Try to set water temperature to a lower setpoint, like 50deg C or so and see if behaviour changes. This will force you to use more water from the hot circuit to have the same temperature out from the mixer tap.

On 2024/06/10 at 1:05 PM, zsde said:

Speculating here, but that may be your temperature regulation valve/circuit of your gas geyser itself that may be faulty, i.e. the temp probe or sensors could be defective or an internal mixing/regulating valve.
Alternatively, is it possible that your mixer taps may be interfering with the water temp regulation of the geyser where changing water pressure between cold and hot created by the mixer tap possibly affects the geysers internal temperature regulation?
Maybe check with the Geyser manufacturer/supplier what the possible cause could be.

 

You get geysers that only offer single use temp control and you get multi-use.

Could you have a model that does not provision for this?

https://dewhot.co.za/wp-content/uploads/2024/06/How-to-choose-your-gas-geyser.pdf

At family holiday house we have gas hot water to some bathrooms and it is battle to get to a comfortable shower temp and have it stay there.    A plumber told me the problem is the showers have mixer type taps (swing for temp and pull for volume).    Do you have a bath with separate hot and cold taps (even if they combine where it runs into bath) and does it also have the problem?

Plumber said there is way to have equal hot and cold temp but then the cold supply at gas geyser must also be the cold supply to the point of use and there is a then a gadget that ensures pressure to gas geyser is equal to the cold water that carries on to point of use.

We’re considering chopping out the damned mixers and replacing with plain old two tap system.

What model do you have?

Do you still have them set to 65C?

 

I have 2 Dewhot Constant temp geysers, which I set to 50C during winter and 45C during summer. I have mixer taps throughout the house and flat and have no issues with hot water

We had same problem. Back pressure from mixer/shower head causes temperature fluctuations. I opened the shower head and removed all restricters(little filter with a lot of tiny holes at supply line)