How are these vented?

[Custom45]

The over sink hot water heaters, they are basically small immersion heater tanks aren't they? How are they vented to stop.pressure building up inside as it heats? Is it through the outlet pipe?

 

[oldbuffer]

1. No, through the inlet pipe on units up to 15 litre capacity. There must be a certain length of pipe between the last cold outlet before the unit (up to 4.5 metres for a 15 l) and NO valve or non-return valve before that outlet.
2. Some can have expansion valves and use a tun dish to show when the the valve operates. Excess water goes to drain.
3. Some have special taps that accommodate the expansion by "dripping" as necessary.

 

[denso13]

Is it through the outlet pipe?

Yes, at least on the ones I've seen.

 

[denso13]

This is from a Santon manual;

3.1 LOCATION
3.1.1 Inlet must always be on the right.
3.1.2 The outlet of this water heater acts as a vent and must not be blocked or restricted in any way.
3.1.3 Only use Santon open outlet spouts.

 

[Custom45]

Thanks Denso, just seen that on the unit. It's a very, very faded label that's barely visible, if I hold it at a certain angle though then I can read it, says what you just said, that outlet is the vent and not to block it or use a tap on the outlet.