Fixing a safety valve leakage?

Question

I'm having a problem with the safety valve/drain which is placed between the main water valve (which controls the water entering into the house) and the boiler/heater. At night - and this only happens at night, after 9 p.m. - the valve leaks, draining excess water into the outside sewage drain. This is obviously beacause of excess water pressure. So my questions are:
-should I replace the safety valve/drain? It's pressure rating is 7 bars
-Any other way of reducing the water pressue w/o replacing the valve?
-Any idea why this only happens at night?

Some additional details:
-It's a wall-mounted gas boiler
-It does have a pressure gauge attached?
-The pressure is correctly set to the manufacturer's instructions (between 1 and 2 bars)
-The problem happens when the system is switched on and off - however, the leak is considerably less when water is flowing through the boiler

Answer 1

I am assuming you have an unvented hot water cylinder. If this is the case, you probably have a problem with your pressure reducing valve, this should be on the mains pipe feeding your boiler and is designed to stop the pressure rising above a set valve (5 bar?), this is easily replaced.

To answer the question about it only happening at night... well it's down to water usage, at night very few people use water, causing the standing pressure of the mains to rise. The pressure rise at night must be very substantial where you are.

If you don't have an unvented cylinder what I said is bollocks, but a pressure reducing valve fitted to your mains pipe should still help you out.

Answer 2

I imagine its happening at night because the pressure building up to above the leakage pressure of the safety valve. There are a couple of things you can try. No 1 try turning the safety valve spindle on its seat it may help it to reseat . An other is to try lowering the boiler pressure. Your boiler may require its pressure cut out setting lowered to stop it getting above safety valve leak pressure. This is usually done by adjusting a srewed pressure switch on the boiler. Hope this helps.

Answer 3

1-Before replacing it , you can try to clean the seat
2-Is this adjustable type (with adjustable nut or bolt ),if so rotate nut or bolt clock-wise direction to increase set pressure ,( you need pressure gauge ) to check and calibrate new set pressure
3-If this safety valve ( thermal/pressure) type with manual relief lever ,try to lift and lower this lever several times to allow deposits to be purged out (this isn't adjustable type)
4-Install pressure reducing valve on pipe feeding heater to adjust and control heater pressure (should be less than) safety valve set (actual) pressure
5-At night city water pressure becomes higher due to minimum rate of water consumption at this time
For more information contact me to answer any question

Answer 4

what kind of boiler is it?
does it have a pressure gauge attached?
is the pressure correct according to manufacterers instructions?
is the problem happening when central heating system is switched on?

Answer 5

replace the valve, its weakened over time. reducing pressure reduced the amount of hot water available to use

Answer 6

put an expansion tank before the water heater, the reason it happens at night is becuse there is less water useage in your area and this creates to much city water pressure.

Answer 7

the water heater could be getting too hot,they usually have a thermostat.the water could be expanding at night because of low or no use,check the water temp and adjust thermostat if too hot.

Answer 8

Maybe your neighbour has secretly tapped into your hot water pipes and is having free bath tubs of hot water every night?

Answer 9

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