Where is my water going?

[oldsalty]

Hi,

I have a Baxi 105HE Instant of 2006 vintage (the one with the pre-heat utility). It is working PERFECTLY except that it seems to be losing system pressure - according to the dial.

Not being one of you guys, so I might be misunderstanding it, this means to me that the water I am putting into the system virtually every other day to top up the system pressure MUST be leaking out of the system.

My problem is that I cannot, for the life of me, detect any wetness at any of the radiators or any of the pipework anywhere in the house where that water is going - there should be something wet, somewhere, if there is a leak?

There must therefore, common sense tells me, be another reason for the Baxi 105HE Instant to be losing system pressure in the way mine is doing?

Help!

 

[Geordie Spark]

Hi,

I have a Baxi 105HE Instant of 2006 vintage (the one with the pre-heat utility). It is working PERFECTLY except that it seems to be losing system pressure - according to the dial.

Not being one of you guys, so I might be misunderstanding it, this means to me that the water I am putting into the system virtually every other day to top up the system pressure MUST be leaking out of the system.

My problem is that I cannot, for the life of me, detect any wetness at any of the radiators or any of the pipework anywhere in the house where that water is going - there should be something wet, somewhere, if there is a leak?

There must therefore, common sense tells me, be another reason for the Baxi 105HE Instant to be losing system pressure in the way mine is doing?

Help!

Have you checked the pressure relief valve??

This is the one that discharges through the wall to the outside of the building.

Under normal conditions there should be no water coming out of it, but the guts of the valve is just a rubber plug on the end of a spring and through time the rubber plug breaks down & allows water to pass.

£6-56 from here IF you need it; Baxi 248056 Combi 80E 105E Pressure Relief Valve PRV

 

[dcelectrical]

if it is discharging you might be able to twist (red or black knob) once and the valve will re-seat itself, it will eventually require changing - one of the things to remember is, when you have been refiling your system you have been using nice clean fresh water and the inhibitor in your system is being diluted, so you will need to top this up too.

 

[Geordie Spark]

if it is discharging you might be able to twist (red or black knob) once and the valve will re-seat itself, it will eventually require changing - one of the things to remember is, when you have been refiling your system you have been using nice clean fresh water and the inhibitor in your system is being diluted, so you will need to top this up too.

This inhibitor is very easy to add through the bleed nipple of a radiator using a normal sealant gun. No mess-no fuss. Perfect for sparkies & others who are not familiar with the finer points of Plumbing & Heating :laugh:

PC200 Central Heating System Concentrated Inhibitor Easy to Use Cheapest 310ml | eBay

 

[chris murphy]

"Hello All",

Good advice from the Members Geordie Spark and dcelectrical above regarding checking the Pressure Relief Valve [PRV] and about replenishing the Heating system Corrosion Inhibitor.

Although the PRV may be dripping at all times ? - if not it should also be checked when the Heating system has been running for enough time to get Hot and the water pressure raised on the pressure gauge.

Although either scenario may not be the cause in this case - the problem of a Pressure Relief Valve dripping or discharging a larger amount of water when the Heating system gets Hot can sometimes be caused when EITHER the Expansion Vessel pressure charge has been lost or lowered - OR there are a large amount of Radiators / the System water content exceeds the maximum amount of water that can be accommodated by the System / Boiler Expansion Vessel.

When either of these situations happen because the expanded water volume cannot be accommodated the Pressure Relief Valve does its job and expels enough water to lower the volume in the system - and the pressure - this shows on the Pressure gauge especially when the system is Cold and people keep topping up the System water.

When either of these situations exist the Pressure Relief Valve does not usually drip or discharge until the system is re-pressurised / water volume increased and the Heating system heats up again - then the expanded water is discharged again.

But Pressure Relief Valves are `notorious` for dripping after a discharge event - they can sometimes be `reseated` as mentioned by Member dcelectrical - but sometimes this does not work - usually depending on the age of the PRV and the state of the plug / washer and how it was seating before the valve discharged - any build up of system debris on the plug / washer can cause a problem with the valve not reseating / dripping.

I believe that the Baxi Combi Instant 105 HE has a Heating system maximum water content of 80 Litres.

BUT - these larger Heat output Combi`s [approx. 30 KW instead of approx. 25 KW] are sometimes installed with the maximum Heat output [or more] demanded by the amount of Radiators in large Homes / Properties and depending on what type of Radiators are installed this can mean that the system water content far exceeds the maximum content accommodated by the Combi`s Expansion Vessel.


Some Years ago Barlo Radiators used to have almost DOUBLE the water content of for example Stelrad Radiators - and other Manufacturers Radiators water contents often varied considerably compared to each others - Heating system efficiency regulations caused Manufacturers to redesign their Radiators to get rid of that ridiculous situation.

I just wanted to post this in case it might be helpful for Members or other readers in future - although IF the situation that I describe above is suspected [system water content possibly exceeds Boiler expansion vessel maximum] the System / Boiler Expansion Vessel pressure should be checked and the System water content should be accurately calculated - BUT - it could still just be a faulty Pressure Relief Valve.

Regards,

Chris

 

[solarsavings]

It could be the primary heat exchanger leaking. With boiler turned off and re-pressurised check the condensate trap/discharge pipe.

 

[Geordie Spark]

"Hello All",

Good advice from the Members Geordie Spark and dcelectrical above regarding checking the Pressure Relief Valve [PRV] and about replenishing the Heating system Corrosion Inhibitor.

Although the PRV may be dripping at all times ? - if not it should also be checked when the Heating system has been running for enough time to get Hot and the water pressure raised on the pressure gauge.

Although either scenario may not be the cause in this case - the problem of a Pressure Relief Valve dripping or discharging a larger amount of water when the Heating system gets Hot can sometimes be caused when EITHER the Expansion Vessel pressure charge has been lost or lowered - OR there are a large amount of Radiators / the System water content exceeds the maximum amount of water that can be accommodated by the System / Boiler Expansion Vessel.

When either of these situations happen because the expanded water volume cannot be accommodated the Pressure Relief Valve does its job and expels enough water to lower the volume in the system - and the pressure - this shows on the Pressure gauge especially when the system is Cold and people keep topping up the System water.

When either of these situations exist the Pressure Relief Valve does not usually drip or discharge until the system is re-pressurised / water volume increased and the Heating system heats up again - then the expanded water is discharged again.

But Pressure Relief Valves are `notorious` for dripping after a discharge event - they can sometimes be `reseated` as mentioned by Member dcelectrical - but sometimes this does not work - usually depending on the age of the PRV and the state of the plug / washer and how it was seating before the valve discharged - any build up of system debris on the plug / washer can cause a problem with the valve not reseating / dripping.

I believe that the Baxi Combi Instant 105 HE has a Heating system maximum water content of 80 Litres.

BUT - these larger Heat output Combi`s [approx. 30 KW instead of approx. 25 KW] are sometimes installed with the maximum Heat output [or more] demanded by the amount of Radiators in large Homes / Properties and depending on what type of Radiators are installed this can mean that the system water content far exceeds the maximum content accommodated by the Combi`s Expansion Vessel.


Years ago Barlo Radiators used to have almost DOUBLE the water content of for example Stelrad Radiators - Heating system efficiency regulations caused Manufacturers to redesign their Radiators to get rid of that ridiculous situation.

I just wanted to post this in case it might be helpful for Members or other readers in future - although IF the situation that I describe above is suspected [system water content possibly exceeds Boiler expansion vessel maximum] the System / Boiler Expansion Vessel pressure should be checked and the System water content should be accurately calculated - BUT - it could still just be a faulty Pressure Relief Valve.

Regards,

Chris

Evening Chris ..... Nice of you to drop in! :welcome:

 

[Geordie Spark]

OK ..... Having had another think about it after reading Chris's post I'm now thinking:

1: Check radiator valve stem glands - wipe a bit of unused (that's important!!) British Standard bog roll all over the valve paying particular attention to the valve stem (that's the bit with the knob on it. ) and look for damp patches.

2: Check the Pressure Relief Valve by finding the bit of pipe that stick through the outside wall - again using the bog roll trick- it should be bone dry. If it's leaking replace it. As Chris mentioned above, you can fiddle about & get it to seal again but for how long?

3: I'm thinking this boiler must be a fair age and maybe it has lost pressure in its Expansion Vessel. This is a vessel that is usually painted red and shape like a Wok. It has a Schrader valve (car tyre valve) sticking out of it and you use this to add air into the vessel by using a bicycle pump. That's the easy bit but you need to know what the pre-charge pressure should be first. From memory, I'm thinking about 0.5 bar with the system empty.

4: This is the one that you don't want it to be - the failure of the Expansion Vessel which means replacing it and it's right at the back of the boiler and a bitch to do. HOWEVER all is not lost as nobody has said that the Expansion Vessel HAS to be inside the boiler. This means you can add it at any convenient point in the heating circuit.

This is the genuine article hiding in the boiler >>>>> https://www.google.co.uk/search?q=p...57.20728j0j7&sourceid=chrome&es_sm=0&ie=UTF-8

And this is what you can replace kit with and fit anywhere you like in the heating circuit. https://www.google.co.uk/search?q=p...57.25030j0j7&sourceid=chrome&es_sm=0&ie=UTF-8

I have fitted and serviced a lot of these boilers including one in my own house and one in my Mother's house and have had to replace Pressure Relief Valves and Expansion Vessels among other things. I liked them and intended to fit one in my present house but got made an offer I couldn't refuse on a stonking Worcester.

 

[chris murphy]

OK ..... Having had another think about it after reading Chris's post I'm now thinking:

1: Check radiator valve stem glands - wipe a bit of unused (that's important!!) British Standard bog roll all over the valve paying particular attention to the valve stem (that's the bit with the knob on it. ) and look for damp patches.

2: Check the Pressure Relief Valve by finding the bit of pipe that stick through the outside wall - again using the bog roll trick- it should be bone dry. If it's leaking replace it. As Chris mentioned above, you can fiddle about & get it to seal again but for how long?

3: I'm thinking this boiler must be a fair age and maybe it has lost pressure in its Expansion Vessel. This is a vessel that is usually painted red and shape like a Wok. It has a Schrader valve (car tyre valve) sticking out of it and you use this to add air into the vessel by using a bicycle pump. That's the easy bit but you need to know what the pre-charge pressure should be first. From memory, I'm thinking about 0.5 bar with the system empty.

4: This is the one that you don't want it to be - the failure of the Expansion Vessel which means replacing it and it's right at the back of the boiler and a bitch to do. HOWEVER all is not lost as nobody has said that the Expansion Vessel HAS to be inside the boiler. This means you can add it at any convenient point in the heating circuit.

This is the genuine article hiding in the boiler >>>>> https://www.google.co.uk/search?q=p...57.20728j0j7&sourceid=chrome&es_sm=0&ie=UTF-8

And this is what you can replace kit with and fit anywhere you like in the heating circuit. https://www.google.co.uk/search?q=p...57.25030j0j7&sourceid=chrome&es_sm=0&ie=UTF-8

I have fitted and serviced a lot of these boilers including one in my own house and one in my Mother's house and have had to replace Pressure Relief Valves and Expansion Vessels among other things. I liked them and intended to fit one in my present house but got made an offer I couldn't refuse on a stonking Worcester.

"Good Evening Geordie Spark",

More good advice from You and Member solarsavings suggestion is also worth looking at.

When I wrote my message I was not trying to answer the OP`s question as I knew that You were responding to Him and that you would suggest some things to check - plus other Members were responding.

I just wanted to explain what I wrote as some Heating system water discharge situations can often be mistaken for just a faulty Pressure Relief Valve.

Although the PRV would obviously the easiest thing to replace if it was the cause - rather than rectifying the situations that I described - although as You mentioned re-pressurising the Combi Expansion Vessel can be done reasonably easily and if necessary adding an Expansion Vessel elsewhere on the Heating system can be done.

I have come across the situation of too many Radiators / excessive system water content installed on Combi Heating systems and other Boiler sealed systems quite a few times - often where other `Engineers` had not known / realised this - and usually constituting too much Heat demand for the Combi`s / Boilers.

I worked on a couple of systems where the installers had fitted 20 or more Radiators / 44 KW Demand [approx. 150,000 BTU`s] or more to a 30 KW Combi Boiler system.

I will be interested in seeing what oldsalty / the OP finds is causing His Combi / Heating system water pressure problems.


"Have a good Sunday"

Regards,

Chris

 

[Geordie Spark]

Has anybody seen the OP lately??? .:juggle2:

 

[oldsalty]

Hi,

First, apology for not coming back sooner. Very many thanks for your helpful comments.

Should have mentioned in OP that I had checked PRV outlet pipe which is absolutely bone dry.

I read all the responses with great interest but I get back to my original point about the water. It is, I assume, water that keeps the needle on the pressure gauge between the two green lines so if the needle moves to the left the pressure is going down and, again I assume, that it is losing water that causes that, making it necessary for me to use the loop to put more water in to bring the pressure back up.

As I said, I have checked all rad connections points and none are wet - I actually used blue paper towels because they show up water much better than white (or even brown!) toilet paper.

Responders have said that all of the bits on the boiler are inside the boiler so if the water was leaking from the expansion chamber or the heat exchanger then, common sense says, there would be water dripping down on the kitchen worktop due south of the boiler - there is none!

I have had one further thought about the pre-heat, which I use a lot, turning it on and off to heat up the water before turning on the tap and wasting, in the case of the upstairs bathroom, 7 litres of water before it gets warm. By using pre-heat I get hot water after only 1.5 to 2 litres - those of you guys on a water meter will know why I do that. I do NOT leave the pre-heat on 24/7 because of the huge amount of gas it uses continually heating up the water that goes cold since the last time it fired up to pre-heat it - precisely why I moved to combi boilers (heat it as you need it) MANY years ago.

My thoughts about the pre-heat raised a question about any POSSIBLE link between the supposedly sealed heating system and the DHW preheat system. I understand the water storage for the preheat is inside the expansion vessel which is where I understand the pressure for the heating system is maintained?

I may be completely off the mark here but if I am proved to be (somewhat) right does that mean I can get my own gas safe registered number and badge?

 

[Leesparkykent]

Radiator pipe work could be leaking on ground floor so would go unnoticed. Do you have floor boards on the ground floor?

 

[oldsalty]

Radiator pipe work could be leaking on ground floor so would go unnoticed. Do you have floor boards on the ground floor?

no, 1995 build, solid floors covered with floating polystyrene and t and g chipboard.

 

[Geordie Spark]

Radiator pipe work could be leaking on ground floor so would go unnoticed. Do you have floor boards on the ground floor?

Ok .... don't go riipping floor boards up yet!

To prove if the pipework under the floor is leaking or not, turn off the isolating valves on the Flow & Return legs on the boiler.

If the pressure drops it proves the "leak" is somewhere in the boiler and not in the pipework to the radiators.