Santon Unvented Water Heater

1 Feb 2009
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United Kingdom
We have a Santon Unvented 15L hot water heater in our toilets at work, there is water slowly dripping out of the overflow and can be seen dripping into the tundish, my boss has been told that its the expansion relief valve or the expansion vessel and wants £300.00 to change them over.

Is there any way of testing this and is that price to change those parts a good price, our company uses an outside maintenance firm and personaly i think the price is a bit steep as there must be 1 or the other part that has gone?

Any help on this would be appreciated, cheers in advance

PS the system is a Santon Aqualine its about 10 to 15 years old and not had any trouble with it until now.
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Would need to know the exact model, but a TPRV for one of this series is £148 retail plus VAT
Often a failed exp vsl will result in the press relief vlv leaking and, if this happens for some time the valve will not re- seat, so needs replacing.
The exp vsl can easily be checked. With no pressure in system check pressure on schrieber valve. It should be whatever it says on the side. If its removed and stays full of water its had it. Also water squitring from valve when pin is pushed in is a sign its diaphragm is punctured.
Most common cause for leaking wtr heaters is no pressure reducing valve fitted.
Hi Dave, are you saying its the Temperature Pressure Relief Valve and not the Expansion Relief Valve & Expansion Vessel?

BTW the model is Santon Aqualine AL153 15L 3kw just not sure of the year but they are old.

Is there any way of testing them?

Many thanks
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I'm not really saying anything for certain as I'm not there to prove the fault.

The TPRV is the only safety valve on this according to the breakdown.

As said it is around £144 + VAT (not £148 :oops: ) retail.
Thanks to all of you who have helped me out on this subject however i am still no closer to the solution?

We have these Santon Aqualine unvented hot water heaters in our toilets at work, one is leaking out to the overflow, i have put a tyre pressure gauge on the expansion vessel to measure the pressure but cant get a reading at all so i pushed in the valve to see if water or air would come out but got nothing at all no water and no hiss of air? what could be the problem here as this is also the same with the water heater in the ladies exact same model but the ladies is not leaking water out?
So i switched off the cold water supply to the heater and drained the water by turning on the hot & cold taps (yeps i also switched off the leccy switch to the heaters) then tried to take a pressure reading again, still nothing so i asked one of my colleagues to lend me his bike pump and connected it up and tried to put some air in the cylinder? big problem here as there was no way air would go into the cylinder it was like the valve just would not let air in or something? conclusion have i done something wrong or is the expansion vessels kaput, PS this was the same on both vessels but only the gents is leaking water into the overflow.

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