Leaking Ariston 2kW Water Heater.

You don't state the size of the heater but under 15l doesn't require G3, notification, blah blah. Indeed the pipework can take care of the expansion but you have to have enough of it. I have found that the insulating FI supplied are a leak prone PIA, is that where the leak is?

If already leaking it probably wont blow up.

The leak might however get worse and should not be ignored. I would recommend replacement of the water heater, and that great care should be taken to follow the instructions TO THE LETTER regarding correct installation of the replacement.

Depending on the water supply pressure, a pressure reducing valve may be required. Fit one if in doubt. Depending on the pipework design, an expansion vessel might be needed.

These unvented water heaters do require following the instructions in EVERY DETAIL and not the common approach of “that is how we normally do it, and will be OK”

Grumpy: 
 

You don't state the size of the heater but under 15l doesn't require G3, notification, blah blah. Indeed the pipework can take care of the expansion but you have to have enough of it. I have found that the insulating FI supplied are a leak prone PIA, is that where the leak is?

I agree with Grumpy.

The pipework can deal with the expansion as in stopping hot water coming out of the cold tap so long as there’s three metres or so from where the water heater is tee‘d off, as Broadgage says you need to follow the instructions, it sounds like the customer hasn’t followed the instructions and has not installed the pressure relief valve, so may have created issues that need resolving.

Sparkingchip: 
 

Grumpy: 
 

You don't state the size of the heater but under 15l doesn't require G3, notification, blah blah. Indeed the pipework can take care of the expansion but you have to have enough of it. I have found that the insulating FI supplied are a leak prone PIA, is that where the leak is?

I agree with Grumpy.

The pipework can deal with the expansion as in stopping hot water coming out of the cold tap so long as there’s three metres or so from where the water heater is tee‘d off, as Broadgage says you need to follow the instructions, it sounds like the customer hasn’t followed the instructions and has not installed the pressure relief valve, so may have created issues that need resolving.

I was waiting for your reply Sparkingchip. I knew that you were experienced in these matters. What I don't understand is how rigid copper pipe and water can accommodate the expansion. Water can not be compressed we are told, and the pipe is not expandable. Please explain.

Thanks,

Z.

The expansion of the water as it is heated is accommodated by forcing water backwards along the pipe, towards the water companies mains.

A minimum length of pipe is required to prevent heated water either entering the mains, or emerging from cold taps.

broadgage: 
 

The expansion of the water as it is heated is accommodated by forcing water backwards along the pipe, towards the water companies mains.

A minimum length of pipe is required to prevent heated water either entering the mains, or emerging from cold taps.

The customer was talking about the pipe length between the heater and the tap. That confused me.

This is the type of heater involved.

Whilst I hesitate to disabuse Broadgage, I think the instructions require a certain length of pipework (defending on dia) between the heater and the tap. When teeing off the cold main a non return valve is required and this is usually quite close to the heater as you tend to use the cold supply to the sink. 

Zoomy, it's because water doesn't expand all that much between incoming at say 10°C and hand wash at 45°C. Between 1 and 2% I think (Cue MAPJ!) It's the change of phase to steam that usually causes the issues.

Water is pretty incompressible - so even a small increase in volume results in a large increase in pressure - it needs room to expand.

The supply pipework can be used - but the water must be free to flow backwards to the supply mains - any ‘loose jumper’ stop cocks, or check valves, or indeed most water meters will prevent that. The so-many-meters rule is just to prevent the warmed water flowing backwards ending up in the supply to cold water taps - potable water must be kept cool (or heated above 60 degrees) - nicely warm encourages bacterial growth.

   - Andy.

Grumpy: 
 

Whilst I hesitate to disabuse Broadgage, I think the instructions require a certain length of pipework (defending on dia) between the heater and the tap. When teeing off the cold main a non return valve is required and this is usually quite close to the heater as you tend to use the cold supply to the sink. 

If there’s a non-return valve then an expansion bottle is required, as well as the relief valve.

The what if‘s include, what if someone turns the stop tap off, but not the heater and what if a pipe freezes and has a plug of ice in it, then the water cannot push back up the pipework.

One customer was installing a heater himself and asked what to do because the pipework wasn’t going to be long enough, after a discussion he put a loop of pipe behind the cupboards to get the required distance from the tee.