Dissolved Oxygen Or Leak - Gloworm Hideaway 80 Boiler

[Tantric Plumber]

Folks,

Our 1989 Gloworm Hideaway has the CH pump mounted directly above it.

When the pump starts, there is the sound of rushing air, which then "bubbles" into nearby radiators.

The noise only occours at start-up - there are no notable air sounds when the system is running. And it only happens after prolonged use of the water heating. There is no electro-mechanical valve, so, if the radiator valves are open, some heat transfers to the radiators without the action of the pump.

I recently re-routed some piping to a bathroom radiator, which gave me opportunity to drain down add some "Sentinel" X400 sludge remover. A visiting gas engineer had suggested that the boiler sounded fairly sludged. The sludge remover was left in for around four weeks, and the water was quite brown when drained out. One 1ltr pack of Sentinal corrosion inhibitor was added on refilling.

Any new piping done during the move was tested "heated" whilst still accessibile under the floorboards, and was totally dry. We have no stains on ceilings. Yet (!)

There are no "dripping/hissing" sounds from the boiler when running, which might indicate a moderate leak.

My suspicions are;-

1/ The sludge remover was left in a bit too long, and has actually disturbed corroded joint face areas that have started off a leak. The system has, however, always run with some kind of inhibitor.

2/ There is a leak on some of the new piping - unliklely, as no external signs, but always worth considering. The work was at one of the highest points on the system, and no noises can be heard.

3/ There is not enough inhibitor in the system, (11 radiators, some long, some double-row) to purge out the oxygen. But I have my doubts about this. It may be a "first step" to add another couple of litres, I guess, and see if the problem goes away. It may be that the action of the water heating, when the pump is off, is separating oxygen off, which is gathering by the downstream side of the pump, causing the "rushing" nosie on start-up.

4/ After 16 years, it's time for a new boiler anyway, and the sludge remover has only hastened the inevitable.

5/ A small length of push-fit plumbing, added by a "professional" during house extension work nine years ago, and clearly "floating around" under the boards (but inaccessible) has degraded. (I can't understand the rush to "push-fit" - from many years of car work, I know that rubber seals, subjected to heat cycles, degrade over time.)

Any help and suggestions much appreciated. Can anything be added that would seal leaks but not clog the system? This is common practice on car cooling systems, of course.

Despite the screen name, I'm a DIY-er, moderately experienced at plumbing jobs.

TP

 

[Softus]

1/ The sludge remover was left in a bit too long, and has actually disturbed corroded joint face areas that have started off a leak. The system has, however, always run with some kind of inhibitor.

I don't understand why you think that there was sludge if it was always inhibited. BTW, although I usually use Fernox Superfloc, I believe that X400 also comes out brown when you drain a solution of it.

3/ There is not enough inhibitor in the system, (11 radiators, some long, some double-row) to purge out the oxygen. But I have my doubts about this. It may be a "first step" to add another couple of litres, I guess, and see if the problem goes away. It may be that the action of the water heating, when the pump is off, is separating oxygen off, which is gathering by the downstream side of the pump, causing the "rushing" nosie on start-up.

It's more likely that something is corroding, so you could be right about not having enough inhibitor, but I don't understand your theory about purging oxygen.

4/ After 16 years, it's time for a new boiler anyway, and the sludge remover has only hastened the inevitable.

Entirely possible - cleaners are awfully good at turning latent leaks into actual ones.

5/ A small length of push-fit plumbing, added by a "professional" during house extension work nine years ago, and clearly "floating around" under the boards (but inaccessible) has degraded. (I can't understand the rush to "push-fit" - from many years of car work, I know that rubber seals, subjected to heat cycles, degrade over time.)

Hm. Some will know that this is a subject close to my heart, so your snipe at your previous plumber makes me somewhat uncomfortable.

Poking fun at plastic and pushfit is a bit of a cheap shot, and is the kind of view that is almost never accompanied by facts. For example, what temperature is the car seal you're thinking of subjected to, and what chemicals is it exposed to? Compare the answer to those questions with the temperature that pushfit O rings experience, and the fact that they're not abraded and/or exposed to oil, petrol, road salt etc.

BTW, at nine years old, your pushfit fittings are well on the way towards surpassing plain old copper pipe for longevity.

Any help and suggestions much appreciated. Can anything be added that would seal leaks but not clog the system? This is common practice on car cooling systems, of course.

Some people do indeed stick in some Radweld. If you don't have TRVs then maybe this is a worthwhile experiment?

 

[pannierstan]

I think its just the fresh water used to fill the system up which hasnt vented all its air and shutup yet. A poorly configured system will find it very difficult to dispell air.

Stan

 

[ChrisR]

If the plastic pipe were the early non "barrier" type, then it would be a source of oxygen ingress. 10?? years ago?

You don't say whether the noises were there before your treatment, or whether it made any difference.

Softus are you saying you've had trouble with leak sealer and thermostatic rad valves?

 

[Agile]

I would even question the professionalism of any plumber whom you employed if he chose to fit plastic pipe and push fit joints.

It sounds like a quick in-quick out job. Not exactly cowboy but not using the best materials for the job.

Tony

 

[Softus]

If the plastic pipe were the early non "barrier" type, then it would be a source of oxygen ingress. 10?? years ago?

A very good point, and I'm really struggling to remember when the current edition of Hep barrier was released. However, TP said "A small length of push-fit plumbing", which could just mean fittings/couplings and no plastic pipe.

Softus are you saying you've had trouble with leak sealer and thermostatic rad valves?

No - but I thought I'd read on here somewhere that someone [trustworthy] had. It makes a kind of sense, since manual rad valves are rarely open just a tiny amount, but TRVs can spend their lives either side around a narrow opening.

 

[Softus]

I would even question the professionalism of any plumber whom you employed if he chose to fit plastic pipe and push fit joints.

Quite so - but you're biased, blinkered, closed-minded, and probably a bit p*ssed.

It sounds like a quick in-quick out job. Not exactly cowboy but not using the nest materials for the job.

Hm. AFAIK twigs and bird poo are not WRS approved.

 

[Agile]

I had inadvertently typed "nest" inspead of "best".

On my keyboard the "n" and the "b" are beside each other and my touch typing are not always totally perfect.

I dont normally need to spell check and the on site spell checker does not work. It appears to have corrected the mistake but the actual copy is not corrected. I assume its to do with my AOL access and program.

Tony

 

[Softus]

I assume its to do with my AOL access and program.

Jesus H. Christ Agile - it's about time you ditched AOL and all the trouble it causes.

 

[Tantric Plumber]

Thanks, all!

Why sludge remover? A gas engineer identified dull "popping" as he ran the boiler. I found brown sludge in the header tank. The system contains some 25year old radiators. The X400 cam eout brown, but this may be a marketing ploy to make the user think that it's having some effect (!)

Noises? They have diminished now, but not totally gone away. The remaining"popping" may simply be expansion of components.

"Purging oxygen theory":- The air seems to build up adjacent to the pump (directly above the boiler), and "whooshes" as soon as the pump starts. I'm assuming that the oxygen is coming from the boiler area as the hot water tank is heated with the pump off, and the gas rises and sits against the pump vanes.

Push-fit. I re-secured a large radiator during the drain-down to do the bathroom additions, and one of the feeds, using plastic pipe, floated around alarmingly in the (inaccessible) underfloor void, rather like holding a long piece of "divining rod" by the short end. Not good. This stuff should have been secured to something to avoid stressing the joints. My comparision with car rubber seals related to those used in cooling systems, with their exposure to heat cycles, glycol, and extreme temperatures. I have known some to become as brittle as balsa wood. Rubber degrades over time and with heat, and, so, to an extent, does plastic. Not installer's bias, but a fact of chemistry.

Leak sealer. Fernox or Sentinel? Any advantages? I have a few TRVs, so this would be a last resort.

Thanks, folks, once again. I'll keep bleeding, and may try some more X100 or similar. And I'll keep you posted.

By the way, if the boiler is leaking, where would I look to spot any leak marks?

TP

 

[Softus]

Why sludge remover? A gas engineer identified dull "popping" as he ran the boiler. I found brown sludge in the header tank. The system contains some 25year old radiators. The X400 cam eout brown, but this may be a marketing ploy to make the user think that it's having some effect (!)

In that case there has most certainaly been some corrosion. Is your heat exchanger also 25 years old? Does your local water tend towards hard or soft?

"Purging oxygen theory":- The air seems to build up adjacent to the pump (directly above the boiler), and "whooshes" as soon as the pump starts. I'm assuming that the oxygen is coming from the boiler area as the hot water tank is heated with the pump off, and the gas rises and sits against the pump vanes.

You've used the words "oxygen", "air" and "gas", all in one paragraph. If the heat exchanger is scaled then you may well be getting hot spots where the water boils (hence popping sound). What is the route of the pipework above the boiler - what vents do you have?

BTW, my own boiler has been dully popping since I moved in 11 years ago, but the gravity DHW circuit goes nowhere near the pump, so any gas generated by corrosion or boiling goes up the vent. If yours has been badly installed then I doubt that you'll fix it with any chemical additive.

Push-fit. I re-secured a large radiator during the drain-down to do the bathroom additions, and one of the feeds, using plastic pipe, floated around alarmingly in the (inaccessible) underfloor void, rather like holding a long piece of "divining rod" by the short end. Not good.

Not necessarily bad either. I'm not a big fan of using plastic on rad tails, because they're exposed to being butted with hoovers and kicked with shoes, but there's no reason to insist on the rad tail being prevented from moving along the axis of the pipe.

This stuff should have been secured to something to avoid stressing the joints.

I don't see how you can reach that conclusion without seeing the run of pipe, but then I don't understand which joints you believe are stressed.

My comparision with car rubber seals related to those used in cooling systems, with their exposure to heat cycles, glycol, and extreme temperatures. I have known some to become as brittle as balsa wood.

But your dometic heating system is open vented, with water circulating in the temperature range 10°C and 80°C, and never goes below 0°C. A car cooling system is pressurised, and the water temperature inside it varies between -10°C and > 100°C! Also, the seals that harden and leak are the water pump seals, which are also subjected to the friction of the pump shaft. And rad hoses are subject to the pressure of the system.

You're not comparing like with like.

[quote... Rubber degrades over time and with heat, and, so, to an extent, does plastic. Not installer's bias, but a fact of chemistry.[/quote]
Not a fact that I ever disputed, but do you think that copper doesn't degrade, harden, become more brittle, erode, or corrode over time? If so, then you're very wrong indeed.

Leak sealer. Fernox or Sentinel? Any advantages? I have a few TRVs, so this would be a last resort.

I don't know - frankly, I've never tried leak sealant, because I don't offer a warranty for my work with a leak sealer, therefore I cure all leaks by repairing them.

By the way, if the boiler is leaking, where would I look to spot any leak marks?

Once it's thoroughly cooled down, otherwise the water will evaporate before you can see it, but anywhere near where you can see rust or scale deposits.

 

[ChrisR]

my touch typing are not always totally perfect.

ARE it not?

I dont normally need to spell check and the on site spell checker does not work. It appears to have corrected the mistake but the actual copy is not corrected.

Funny that, I wouldn't have expected the spell checker to have done anything about the word NEST!

Keep digging, Tony!

 

[Softus]

Keep digging, Tony!

Chris, you've misspelt the word "drinking".

 

[Tantric Plumber]

Softus,

The heat exchanger is around the same age as the boiler, around 17 years old.

Our water is softish (not much scale in kettles).

"Gas" - just a non-chemist's term for whatever separates from water when it is heated.

The pipe from the boiler to the heat exchanger is tee-d into a vent which exits into the CH header tank. I would have expected any gas to vent out of this.

I don't think it's a design issue, as British Gas supplied the boiler and replaced the cylinder back in 1989 when they still had decent staff. And I've not had the gas noise issue until after I added X400 and flushed twice, and then refilled.

Push fit. Maybe I spent too much time on old steam locomotives, motorbikes, and cars in my youth, but experience has taught me "what does not seem right probably isn't right". I'm perfectly happy to be proven wrong, but I've taken too many thermostat housings apart that had rubber O-rings made brittle by age and heat cycles. Nothing else. And I'm less than happy about anything, pipework or cable, that flaps about under floorboards rather than being secured.

Having said all this, I ran the pump this morning, heards the "whooshing", but then vented very little air indeed from the rads. I've stayed in friend's houses which sounded like they had Flatulent Koi Carp swimming around the system, and where there was a serious leak somewhere. Maybe, after all this, it is simply gas being "boiled out"

Thanks, all, once again, for the kind help.

TP

 

[croydoncorgi]

BROWN sludge means you've got a LOT of oxygen in your system (resulting in full oxidation of steel bits to rust intead of BLACK magnetite, which forms when there's less oxygen present).

Unless you have proof-positive otherwise, I would look VERY carefully for two problems: an air leak near the suction side of the pump, or on the pump valves (favourite is the suction-side valve stem), or circulation through the F&E tank due to 'pumping over' through the vent pipe. These are usually the only problems that add enough oxygen in a short time to cause rapid brown sludge build up. The most frequent cause of pumping-over starting to happen on a system that worked OK before is a blockage in the pipework between the vent and the cold feed from the F&E.