Water pressure on boiler keeps going

Daisy_84

I am having to add pressure almost every two weeks now.

The pressure goes in straight away after I’ve turned the blue lever and the boiler fires up. I don’t even have to do the black leaver. What could this be indicating?

Can someone tell me the purpose of the black lever.

Can someone also tell me the purpose of the blue lever.

I’ve used both levers many times but I don’t know what they actually do.

Ayr_Rage

What boiler?

What does the manual say regarding the coloured levers?

Pictures speak a thousand words so could you add some.

ThisIsWeird

Daisy_84 said:

I am having to add pressure almost every two weeks now.

The pressure goes in straight away after I’ve turned the blue lever and the boiler fires up. I don’t even have to do the black leaver. What could this be indicating?
Can someone tell me the purpose of the black lever.
Can someone also tell me the purpose of the blue lever.
I’ve used both levers many times but I don’t know what they actually do.

Make and model as Ayr has asked, please.

Almost certainly, tho', your black lever is a second, non-return, valve on the top-up loop, and is designed to ensure there's no risk of the sealed 'system' water - which has chemicals in it - getting back into the domestic water. So, boilers either need to have a hose for the topping up - which should be removed after use - or can employ two valves like yours.

You should find that if you turn the black tap, you won't be able to top up your boiler. And when you've finished topping up, you should really close both taps.

But, don't touch the other tap until we confirm that's what it is, and not - say - the gas tap... :-)

Anyhoo, where is the pressure loss? Give me a mo' whilst I copy and paste from another thread :-(

FreeBear

ThisIsWeird said: But, don't touch the other tap until we confirm that's what it is, and not - say - the gas tap... :-)

Gas will (nearly) always yellow.

Blue is generally used for potable water.

Black - dunno.

ThisIsWeird

My gas is yellow too (matron!)

If you are certain, Daisy, that the black tap is on the same wee pipe as the blue, then almost certainly it's the second top-up valve. But don't worry about that for the mo', as it's obviously open and working for refills. So, continue to use the 'blue' for top-ups. But, make and model, please?

Ok, what to do if your boiler is losing pressure...

1) What pressure do you top it up to, and what does it fall to?
2) And - very importantly - what does the pressure do at other times? Ie, does it fluctuate as the system heats up? Does it increase - if so, to what figure?

What have you looked at and checked so far?

The first obvious steps - apart from monitoring what the pressure does in use - is to check the two exterior pipes for escaping water. These are the 22mm white plastic condensate pipe - which probably heads into a drain - and the 15mm copper safety discharge pipe which typically points to the ground.

The former will issue 'slugs' of condensate every few minutes when the boiler is in use, but nothing should come out when the boiler has been shut off for a while. If you can position a cup under there, you can monitor this, say, overnight, if the boiler is off.

The latter - the 15mm copper pipe - should not have anything come out of it at all. Check the end - is it bone dry? The simplest way to monitor this pipe is to rubber-band a clear bag over the end.
These are the basic layman's checks.

In addition, of course, go around every radiator, and examine each rad valve closely. You are looking for wee seeps, but much of this can evaporate as soon as it forms, so might not be obvious. Look for scale and verdigris, for example, around each joint. Look for stains or patches on the floor at the bottom of the pipes. Anything?

A step up from this, but only realistic in summer when you don't need your CH, is to isolate the boiler from the radiators. The 22mm CH 'flow' and ditto 'return' pipes have isolating valves on them as they join the boiler. These can be turned fully off, so isolating the boiler from the rads. If the pressure continues to fall asleep you use your boiler for DHW, the leak must be internal to the boiler. If the drop stops - but then does fall the instant a valve is reopened again - then the loss must be in the pipes and rads. 

An interesting detail you've given - the pressure is restored very quickly when you open the tap - it doesn't appear to take much water? You can hear the refill hiss, and it's quite brief and not gushing?! Priority one - keep a beady eye on the pressure gauge to see what happens after you've topped it up and turn the boiler back on, and observe it as it heats up.

Bigphil1474

I've got a similar sounding problem but not sure if it's the same and don't have a solution yet.

My Ideal Vogue c26 needed topping up a couple of weeks ago as it wasn't coming on due to low water pressure, so topped it up to just over 1 bar. To top it up there is a blue and black tap, turn the blue tap on first and then use the black tap to give little blasts of top up to reach the required pressure. Then turn both taps off. All good. No issues on fire up.

Anyway, I checked on the boiler over the weekend as we're learning how to get the water temperatures how we like them (only moved in a few moths ago) when the heating was on and the pressure was up just over 3 bar, which is a lot higher than any boiler I've ever had. I then checked later when the heating was off, and it was down to about 0.6 bar (just above the red area). I'm thinking that there is some sort of pressure relief which releases pressure when it gets too high, so when the boiler is not being used it then is lower and at some point it's just too low for the boiler and we get the low pressure warning, top it up and repeat? Obviously, something is broken?

ThisIsWeird

Bigphil1474 said:

I've got a similar sounding problem but not sure if it's the same and don't have a solution yet.

My Ideal Vogue c26 needed topping up a couple of weeks ago as it wasn't coming on due to low water pressure, so topped it up to just over 1 bar. To top it up there is a blue and black tap, turn the blue tap on first and then use the black tap to give little blasts of top up to reach the required pressure. Then turn both taps off. All good. No issues on fire up.

Anyway, I checked on the boiler over the weekend as we're learning how to get the water temperatures how we like them (only moved in a few moths ago) when the heating was on and the pressure was up just over 3 bar, which is a lot higher than any boiler I've ever had. I then checked later when the heating was off, and it was down to about 0.6 bar (just above the red area). I'm thinking that there is some sort of pressure relief which releases pressure when it gets too high, so when the boiler is not being used it then is lower and at some point it's just too low for the boiler and we get the low pressure warning, top it up and repeat? Obviously, something is broken?

Perfect symptoms!
These are sealed, pressurised, systems, with a pressure gauge to tell you what's happening inside.
What happens when you heat water? It expands. In a sealed system, this would mean a pressure rise, which is what you are experiencing.
To cope with this expanding water, the boilers are fitted with (on system boilers, externally, on combis, internally in general) an Expansion Vessel.
These EVs have a flexible diaphragm in the middle, with pressurised air (typically around 1 bar) on one side, and a pipe to the system water on t'other.
Now, when the water heats up and expands, it simply passes into this vessel, pushes the dia and compresses the air, and the system pressure should therefore remain pretty constant.
When the system cools and the water contracts, the vessel returns this excess back to the system.
It all goes wrong when that vessel doesn't work... Then you get exactly what you've noticed, Phil - the pressure soars until it reaches around 3bar. That's the safety limit, and a Pressure Release Valve is pushed open, allowing that hot expanding water to be safely ejected out the 15mm copper pipe outside your house. 
What now happens when your system cools down? The water contracts as before, but now there's less water in the system - ergo, your pressure ends up below your starting point.
So, almost certainly your EV either needs attention (perhaps it's lost its air) or is kaput, in which case it needs replacing.
It's competent DIYable, but usually requires the boiler casing to be removed, so I cannot recommend it.

Bigphil1474

Perfect. My amateur sleuthing edged me towards something like that but it's good to hear a quality explanation. I will contact Dave the Plumber today (he's also a Gas Safe Registered heating engineer )

Albermarle

ThisIsWeird said:

Bigphil1474 said:

I've got a similar sounding problem but not sure if it's the same and don't have a solution yet.

My Ideal Vogue c26 needed topping up a couple of weeks ago as it wasn't coming on due to low water pressure, so topped it up to just over 1 bar. To top it up there is a blue and black tap, turn the blue tap on first and then use the black tap to give little blasts of top up to reach the required pressure. Then turn both taps off. All good. No issues on fire up.

Anyway, I checked on the boiler over the weekend as we're learning how to get the water temperatures how we like them (only moved in a few moths ago) when the heating was on and the pressure was up just over 3 bar, which is a lot higher than any boiler I've ever had. I then checked later when the heating was off, and it was down to about 0.6 bar (just above the red area). I'm thinking that there is some sort of pressure relief which releases pressure when it gets too high, so when the boiler is not being used it then is lower and at some point it's just too low for the boiler and we get the low pressure warning, top it up and repeat? Obviously, something is broken?

Perfect symptoms!
These are sealed, pressurised, systems, with a pressure gauge to tell you what's happening inside.
What happens when you heat water? It expands. In a sealed system, this would mean a pressure rise, which is what you are experiencing.
To cope with this expanding water, the boilers are fitted with (on system boilers, externally, on combis, internally in general) an Expansion Vessel.
These EVs have a flexible diaphragm in the middle, with pressurised air (typically around 1 bar) on one side, and a pipe to the system water on t'other.
Now, when the water heats up and expands, it simply passes into this vessel, pushes the dia and compresses the air, and the system pressure should therefore remain pretty constant.
When the system cools and the water contracts, the vessel returns this excess back to the system.
It all goes wrong when that vessel doesn't work... Then you get exactly what you've noticed, Phil - the pressure soars until it reaches around 3bar. That's the safety limit, and a Pressure Release Valve is pushed open, allowing that hot expanding water to be safely ejected out the 15mm copper pipe outside your house. 
What now happens when your system cools down? The water contracts as before, but now there's less water in the system - ergo, your pressure ends up below your starting point.
So, almost certainly your EV either needs attention (perhaps it's lost its air) or is kaput, in which case it needs replacing.
It's competent DIYable, but usually requires the boiler casing to be removed, so I cannot recommend it.

Just to check something with you on some of these points for my own interest ( if I may)
My system boiler has no pressure display/readout, so I have always presumed the external pressure gauge/dial ( below the EV and near where you can top up if necessary) is doing the same job? and that presumably internally in the boiler there must be an internal pressure monitoring system, even though there is no display for one?

I have also a megaflo type tank next to the boiler, with all the usual pipe work involved.
The 15mm copper pipe that goes outside the house is actually plumbed into this pipework, and I presume is the pressure relief outlet for both the heating and the hot water tank. For sure it is not directly/physically coming out of the boiler. Is this normal as you and others often refer to the copper overflow pipe coming directly down out of the boiler ( like the condensate pipe) ?
When I have had water coming out of that pipe in the past it has been related to problems with the megaflo EV rather than the central heating one, but this does not seem to affect the central heating pressure.
So it would seem in some cases, like mine, water coming out of the overflow pipe is not necessarily related to boiler/CH problems. 

FreeBear

Albermarle said: Just to check something with you on some of these points for my own interest ( if I may)
My system boiler has no pressure display/readout, so I have always presumed the external pressure gauge/dial ( below the EV and near where you can top up if necessary) is doing the same job? and that presumably internally in the boiler there must be an internal pressure monitoring system, even though there is no display for one?

I have also a megaflo type tank next to the boiler, with all the usual pipe work involved.
The 15mm copper pipe that goes outside the house is actually plumbed into this pipework, and I presume is the pressure relief outlet for both the heating and the hot water tank. For sure it is not directly/physically coming out of the boiler. Is this normal as you and others often refer to the copper overflow pipe coming directly down out of the boiler ( like the condensate pipe) ?
When I have had water coming out of that pipe in the past it has been related to problems with the megaflo EV rather than the central heating one, but this does not seem to affect the central heating pressure.
So it would seem in some cases, like mine, water coming out of the overflow pipe is not necessarily related to boiler/CH problems. 

There may well be a pressure sensor inside the boiler that can be read via OpenTherm/EMS/eBUS/wotever depending on how old the boiler is. Or it could just be a simple pressure switch that triggers a fault code when it falls below a certain level. The guage below the EV will show exactly the same pressure as any internal sensor.

My boiler doesn't have a vent pipe from the PRV. So if the boiler needs to dump excess water, it will come out of the condensate pipe. Diagnosing a PRV fault isn't going to be straightforward for me.. But I have ways to monitor & record boiler pressure

ThisIsWeird

Albermarle said:

Just to check something with you on some of these points for my own interest ( if I may)
My system boiler has no pressure display/readout, so I have always presumed the external pressure gauge/dial ( below the EV and near where you can top up if necessary) is doing the same job? and that presumably internally in the boiler there must be an internal pressure monitoring system, even though there is no display for one?

I have also a megaflo type tank next to the boiler, with all the usual pipe work involved.
The 15mm copper pipe that goes outside the house is actually plumbed into this pipework, and I presume is the pressure relief outlet for both the heating and the hot water tank. For sure it is not directly/physically coming out of the boiler. Is this normal as you and others often refer to the copper overflow pipe coming directly down out of the boiler ( like the condensate pipe) ?
When I have had water coming out of that pipe in the past it has been related to problems with the megaflo EV rather than the central heating one, but this does not seem to affect the central heating pressure.
So it would seem in some cases, like mine, water coming out of the overflow pipe is not necessarily related to boiler/CH problems. 

The answer to most of that is, er, I don't know. I'm not really familiar with system boilers, tbh, but since they tend to have external pumps and EVs, then I guess it makes sense they have ditto Pressure Release Valves too. But I don't know.

Make and model, Albe?

As for the PRV on the Megaflo pipework, I'd have thought there would be two, one for the sealed 'system' - boiler, rads, heating coil - and another for the Mega itself. I presume it empties via a tundish so any discharge can be seen? If there's only one tundish, can you trace the pipe feeding into it and see if there could ultimately be two?