Pressure Loss - idiots guide !!!

[Troytempest69]

Hi all

New to this site, although already learnt lots going through the other posts. Have an issue with my central heating system & hoping someone could fill in the blanks for me.

System is a Worcester 28i junior, 7 rads, copper pipework, pushfit copper connections throughout (except compression rad valves), and the whole system bar 4 of the radiators were fitted new within the last 18-24 months. The 4 rads mentioned are the old ones I found in the house.

HW has always been ace, but recently the CH has lost pressure (within last 2 weeks). System set to 1bar, and this reduces to about 0 over the course of a few days. Every time I just re-fill system, bleed rads upstairs & all is fine again. (Done this about 4 times in last 2 weeks now)

Few obervations & remdies from reading the other posts...am I going along the right lines???

* I have located a small drip from 1 rad valve (and I mean small), but would this cause such a large (in my eyes) drop of pressure in such a short space of time?

Answer: Fix leak & check to see if pressure loss continuous. Also, double check all other rad valves again. Is it best to check when system is cold,or been on a while?? (Im going along the line that this leak is a co-incidence, not the root cause)

* All the pipework bar a small 4 metre length section is in the ground floor ceiling, and there are no obvious signs from looking at the ceiling of any damp patches, falling plaster etc.

Answer: Lift floorboards on groundfloor to see if 4 m section of underground piperwork is leaking, or if recent cold spell has burst/cracked a pipe & replace/repair as necessary. I REALLY REALLY dont wanna life the flooring upstairs as the whole house has been laminated....bloody stuff!!

*There is no inhibitor in the system. The Corgi chap I had to install the system in put some in, but I drained most of the system a few days later to change a radiator valve......and I never got round to sorting this out.

Answer: When leak finally sorted, get some put in. Also, when I next bleed rads, check 'air' with a match. Am I write in thinking that if it flames its hydrogen thats caused from corosion, but if it doesn't its just normal air caused from suction into the system?? (please tell me I'm not going to 'blow myself up'.

* When the CH is on, the pressure rises gradually to about 2 bar as the rads heat up. From other posts it seems that if it shot up to about 3 there may be a problem with the expansion vessel. Does my system have an EV??

* I need to put a plastic bag over the exit pipe outside to see if the PRV is leaking, or is operation. Is this right??

Right, thats about it. I realise its either a leak with the bolier, or through th pipework/rads. If its the bolier, or if some pipework needs replacing I'll leave that up to BG (I've just signed up to one of their Homecare contracts about a month ago), but if its just a fitting on a rad that needs tightning I'll have a go myself.

Thanks in advance & sorry for being such a duffer!!

Pete

 

[chrishutt]

You're more or less on the right lines. Your boiler does have an expansion vessel (large red thing, probably at back). Leaks are usually from radiator valves, especially the gland seal around the spindle, or within the boiler - check AAV and PRV.

 

[Cohen]

I've recently had a new combi boiler installed and have found that so far every morning I find the pressure is at zero. As such, if I've set the timer to turn the heating on, it won't because there isn't enough pressure. So, I add more water to the system (by opening a valve underneath the boiler) until the pressure gets back into the green section. Within 3 - 4 hours of turning the heating off, the pressure gradually drops back to zero.

I've checked every radiator in the house and there are no leaks on any of the exposed pipework and valves. I've also stuck a large plastic basin (wider than the boiler itself) underneath the boiler and it has stayed bone dry since I've put it in there close to a week ago now.

I've checked the ceiling in every room downstairs roughly below where the pipework had been fitted previously (the radiators and the pipework were untouched during this recent new boiler installation) and there are no signs of leak coming thru. I'm guessing with such a rapid loss of pressure as I've described it must equate to a fair amount of water, which means I would have spotted the leak sooner rather than later in the locations I've already checked. Alas, I've not seen anything and so...

Could there still be a problem within the boiler itself (expansion vessel etc)? Or do I have to start taking up the carpets plus floor boards in the appropriate rooms downstairs to check the pipework there?

 

[chrishutt]

Read my previous post - check AAV and PRV. If you don't know what they are check definitions topic or do a search.

 

[Bryan King]

when checking for leaks, do it when system is cold and increase pressure on system until water flows from pressure relief valve. The high pressur will make it easier to spot any leaks . Make sure you reduce pressure to normal before restarting boiler.

Also Expansion vessel is a good start when pressure problems occur

 

[chrishutt]

increase pressure on system until water flows from pressure relief valve

Do not do this. Once the PRV starts leaking, it may not seal shut again and you will have the additional expense of having a new PRV fitted.

 

[Bryan King]

i wouldnt worry about "maybe,s" unlikely that valve will stick open and lets face it do you wanna cure the problem or tiptoe around it!

Pressure relief valves are not as vulnerable as people would like to think

 

[Bryan King]

chris pressure relief valves should always be tested as part of a boiler service Any one who doesnt test them isnt servicing properly! If a Plumber drains your boiler to work on the expansion vessel he would most probably drain through the pressure relief

 

[Softus]

i wouldnt worry about "maybe,s" unlikely that valve will stick open and lets face it do you wanna cure the problem or tiptoe around it!

Pressure relief valves are not as vulnerable as people would like to think

This is bad advice. There is absolutely no virtue in taking the risk of pressurising until the PRV opens.

chris pressure relief valves should always be tested as part of a boiler service Any one who doesnt test them isnt servicing properly! If a Plumber drains your boiler to work on the expansion vessel he would most probably drain through the pressure relief

This is the same bad advice, expressed using a different set of words.

 

[Bryan King]

sorry but disagree. Safety valves are there for a reason and should not be regarded as a risk when checking there operation.

i use this system on a regular basis and achieve results and i dont keep going back time and time again to the same problem.

Dont be afraid of the Boiler!

 

[Bryan King]

http://home.btconnect.com/centralheating/helpmate/Trades/Central_Heating_combination_Boiler.pdf

 

[Softus]

sorry but disagree. Safety valves are there for a reason and should not be regarded as a risk when checking there operation.

The risk exists, whether or not you regard it as one.

i use this system on a regular basis and achieve results and i dont keep going back time and time again to the same problem.

You "achieve results"? Very odd vernacular for a heating engineer. I smell a rat.

Would you like to illustrate your vague point by stating the number of PRVs that you test, and the proportion of those that you have to replace after testing them?

Dont be afraid of the Boiler!

WTF?

BTW, the mods prefer that we put all words into one posting, rather than append an extra one. In case you didn't know that there's an edit button, there's an edit button, viz:

 

[ACOperson]

I would say that 20% of PRV's let by after use unless you spend time flushing mains pressure water through them and repidly snapping them shut to smash up any system debris caught betewen the valve and seating. Even then only about half of the abouve 20% do not need to be replaced.

If you tell 10% of your customers that they need to replace the PRV following your visit you will not have many customers after a while, as they will wonder why their boiler worked OK until you went there.

How many PRV's do you go to that do not operate when opened / overpressurised?

 

[ChrisR]

pressure relief valves should always be tested as part of a boiler service

Not according to the boiler manufacturers, I think. Name some which do say to do this.

If a Plumber drains your boiler to work on the expansion vessel he would most probably drain through the pressure relief

A plumber might because he knows no better. A boiler engineer would use the drain cock on the boiler, or pipework.

I would say that 20% of PRV's let by after use

I would say that 20% of PRV's DO NOT let by after use !

 

[Cohen]

Read my previous post - check AAV and PRV.

I took the cover off the boiler and had a look at the two things you mentioned and there isn't any leaks or dampness on or around them.