topping up your boiler?

every now and again I have to top up the boiler with water - foe example I don't let it go below 1 on the dial shown on the front of the boiler. Sometimes I top it up to 1.5. I do this by opening a valve which lets water into the heating system. I'm just wondering how often this should have to be done?
 
How often is every now and then? If you need to do this on a regular basis, there's a good chance you have a small leak in the system, coils in the immersion tank are often the culprit.
 
Most pressure losses are due to under-pressurised expansion vessels. I rarely find them set correctly and even rarer are they checked during a service. This is a requirement by the boiler manufacturer, so insist on it when your boiler is next serviced. You will find that your system will perform much better if set correctly.
On the downside, you could also have a small leak or a weap somewhere.
 
Most pressure losses are due to under-pressurised expansion vessels.

Need some help with this.
Day 1, at cold pressure on gauge is 1.5 bar
Day 30 ........0.0 bar, so top up to 1.5
Day 60........etc

So how can an under-pressurised EV contribute to this sequence?
 
Need some help with this.
Day 1, at cold pressure on gauge is 1.5 bar
Day 30 ........0.0 bar, so top up to 1.5
Day 60........etc

So how can an under-pressurised EV contribute to this sequence?
Because when the vessel is deflated, there is nowhere for the heated water to expand to and it usually goes out through the PRV when hot. It then cools returning to a lower pressure than previous and the sequence repeats itself.

It is the most common reason for low pressure issues in heating systems.

In order to check the EV pressure, there must be no system pressure against it, so the boiler must be drained to do this.
 
It sounds similar to an issue we had with our boiler. The expansion vessel had blown, and needed to be replaced.
 
It sounds similar to an issue we had with our boiler. The expansion vessel had blown, and needed to be replaced.
Usually no need. If you de-press the schrader valve and if water comes out, the internal diaphragm is split. It air or nothing comes out, it just requires re-pressurising with air. However, I normally replace the schrader valve whilst I'm at it, as this is usually the culprit for the loss of pressure in first instance.
Same as a car tyre, hence the tyre guys always replace them when working on tyres.
 
Because when the vessel is deflated, there is nowhere for the heated water to expand to and it usually goes out through the PRV when hot. It then cools returning to a lower pressure than previous and the sequence repeats itself.

It is the most common reason for low pressure issues in heating systems.

In order to check the EV pressure, there must be no system pressure against it, so the boiler must be drained to do this.

The learning continues: thank you
 
Usually no need. If you de-press the schrader valve and if water comes out, the internal diaphragm is split. It air or nothing comes out, it just requires re-pressurising with air. However, I normally replace the schrader valve whilst I'm at it, as this is usually the culprit for the loss of pressure in first instance.
Same as a car tyre, hence the tyre guys always replace them when working on tyres.

We have an overpriced, not very good Italian brand of boiler which doesn't have readily available parts. The plumber said the EV on that could be repaired, but it would be a lot cheaper, quicker and more effective to just add a new vessel to the system
 
We have an overpriced, not very good Italian brand of boiler which doesn't have readily available parts. The plumber said the EV on that could be repaired, but it would be a lot cheaper, quicker and more effective to just add a new vessel to the system

That does not make sense. The only way you can repair an EV is replace the schrader valve and fill back with air. Air is free and schrader valves are pence.

Also you must maintain the boiler vessel as regulations state that there shall be no valve between the heat exchanger and the means of expansion. Your boiler has 2 valves below, therefore you just maintain the vessel within it.
It is there for a reason....

Incidentally which boiler do you have?
 
Hi, my boiler was down less than 0.5 bar and so I found the fill loop etc and topped up the system.. Except it's gone over 3 bar now... Is this dangerous.. Won't put boiler on just in case :(
 
Drain some water from a radiator bleed screw into a pot until the pressure reaches 1.3 bar.

Don't turn on until you do this otherwise it will over-pressurise when heated.
 
What would happen if you put it on with too much or too little pressure?
Assuming it's a gas boiler, it won't fire if low pressure but if over-pressurised, the 3 bar safety valve will open and empty water from the system. If there is any debris in the heating system, such as magnetite, the safety valve seal may not re-seat and continue to leak. It can also lead to damage to the expansion vessel.
 
Hi there. Don't want to have to resurrect this post, but I also do...
I'm getting a pressure problem on the gas boiler. (error F.75 on Glowworm 18s) which I've been told means I have to top up the heating system by a plumber who doesn't want to come out and fix it. The pictures are my selection of taps. Which ones do I mess with? Thanks. Also I can bleed rads. Hot press is upstairs and boiler is in the kitchen downstairs.
 
My guess is that it's the black one or the red one directly underneath it in the first picture as they are both closed. You could try opening one for 10 seconds and then close it again to see if it makes a difference on the pressure gauge on the boiler. If it doesn't work, try the other one.
 
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