British Gas Combi Quote !!

[chrishutt]

Most of the iron oxide sludge in existing systems will be found settling at the bottom radiators and coating pipe walls, etc. The actual circulating water can appear quite clean but is no indication of a clean system.

I flush systems with mains water pressure, first draining radiators so that the flush runs through the bottom channel of the radiator, one rad at a time. This will invariably shift black sludge, even on a relatively new and clean system.

If this iron oxide isn't removed it will be liable to circulate with the water and end up causing problems in the new boiler. Perhaps if a Magnaclean or similar is fitted to the return one might get away with only a quick flush without chemical cleaning.

 

[sambotc]

Agreeing to disagree here. We normally run the sentinel cleanser through an old system using the old boiler before draining and replacing. If running the system doesn't stir up the black then the boiler operating normally wont either.

After the new boiler is fitted we hot flush to ensure any flux is removed and the water normally still comes out clean.

Perhaps the powerfluch machine is removing more, but perhaps it is also stirring up what would otherwise not circulate.

I do own a powerflushing unit, but for combi chop's rarely use it for the previous reason's. As said before we are fitting these spira-vent's now which also act as a debris collector.

Also as said before if the system isn't regularly being topped up then how iss iron oxide going to be produced to a point where it becomes a problem?

Sam

 

[Blasphemous]

That Sig Chris...
__________________
It's TRVs, not TRV's.

They'll all listen eventually

 

[chrishutt]

That Sig Chris...
__________________
It's TRVs, not TRV's.

They'll all listen eventually

Well it clearly didn't cut any ice with sambotc. He managed to use apostrophes in plurals 3 times in just two sentences.

If running the system doesn't stir up the black then the boiler operating normally wont either.

I think you're making a big mistake there. Flow rates through the bottom of radiators can vary, particular as TRVs close down other rads. Also If air collects in the rad and obstructs circulation through the top channel the bottom channel will receive the full force of the pumped flow. This would only have to happen once to dislodge a load of sludge which might end up blocking the DHW heat exchanger.

Mains flushing is quicker and simpler to carry out than "power flushing", yet can be just as effective. A basic flush could be done within an hour or so, which would remove the bulk of the sludge settling in the base of the radiators. Failure to flush the system adequately could invalidate the boiler guarantee and means that you are not installing the boiler in compliance with the Building Regulations.

 

[sambotc]

Firstly i thought this forum was do with plumbing not an assessment on your english skill's?

Secondly i agree that flushing is necessary My argument was that i think powerflushing is/can be a con for customer's as it all looks very professional standing there with a machine for 10 min's on each rad etc, but in actual fact may not be required. This is especially the case on sealed systems, where there is a very limited supply of oxygen in the water to cause sludge build up's unless the customer is having to top up water (therefore re-oxygenating the water) due to a leak. In which case you would want to find the leak before powerflushing.

Combi's have been around for a good few years now, i change 1 a week on average, as i said before i rarely see or hear of many which have had blocked heat exchangers etc but maybe i'm just lucky?

Just my opinion though, Sam

 

[webrits]

i pay about £300 labour to swap a boiler over. my boliers are about £600. so i am looking at £1k tops. based in yorkshire so BG are big rip off merchants. i am a private landlord, so not putting in the top boilers. usually potterton

Bet they're not power flushed and commissioned properly at this price either

Correct, power flushing was not included, they were just going to fit the magnet device (magflow??).

 

[namsag]

Think people should read what sambtoc actually wrote instead of checking his gramma .
He said power flushing on a SEALED system that has not been subject to constant filling of fresh oxygenated water was not required he didn`t say flushing was not required,to remove installation debris flux etc

It is basic chemistry for anything to oxidise oxygen is required so after flushing initial filling and inhibitor added where is the oxygen going to come from to cause oxidation(rust magnetite etc).

Power flushing is one of the biggest cons out there, not saying it is not required on certain systems but no way is it required on the amount that it gets done on.. Amazing how many are done on gravity systems because a 5 quid anti gravity valve has seized. Prices some firms charge it would be cheaper to renew rads and the sections of offending pipework

 

[chrishutt]

maybe i'm just lucky?

Maybe you're just unaware of what's causing combis to fail so frequently that you have to replace one a week. All the manufacturers and most experienced installers stress the importance of thoroughly flushing the system. Perhaps they know something that you don't?

 

[nickso]

im far from being an expert on powerflushing but......

several water samples that i have taken and subsequently sent for analysis have shown various nasties in the water and the lab have recommended a flush. none of them were due to large amounts of particles or sludge, some were clear water.

 

[sambotc]

I change combi's for warmfront grant's so it has no influence on me as to why they have broken down, usually they haven't actually.

Glad namsung can see where i'm coming from and can see through the marketing con which powerflushing has created only over the last few years. This is what installers have now twigged onto (british gas for example) and can sell a powerflush to a 3 year old vokera combi system because the diverter has seized. Of course this MUST be sludge, not the fact the boiler manufacturers have created unreliabe parts. All my job's get flushed, but using the conventional method, not heard of any problems so far.

If i found a sludged up sytem which had always worked on a sealed basis i would recommend finding the leak which would fix the problem permenantly along with inhibitor, not powerflush and leave to build up again. Powerflushing would then be considered after this.


Sam

 

[namsag]

Nickso that is why on completion of a system you hot and cold flush using a chemical such as x300 and then inhibitor .

 

[sambotc]

Nickso that is why on completion of a system you hot and cold flush using a chemical such as x300 and then inhibitor .

Or get the powerflush machine out for an extra £350

 

[ChrisR]

I'm not actually just trying to agree with everyone but the variations expressed in this thread do cover most situations, imho. MOST systems have some crud in them and eventually it can affect secondary heat exchangers, or the preference for the water to go one way round the system over another.
I've known combis on slightly grubby systems where I did no flushing, not give any trouble after say 8 years of being in touch with them, but another new system, where I did everything by the book need the 2ndry hex cleaning after 4-5 years.

Yes I do find mains flushing very useful. VV good on old gravity systems. Also on closed systems where you can let some pressure build up in empty rads; when you release the pressure through a rad you want to clean you get a phenomenal flow rate!
SOme powerflushers have very low pressure pumps, less than 1 bar, which seems daft.
Yes if you leave something like X400 or Superfloc in for a good time, a lot more dark matter appears, when a reversing powerflusher is applied, than mains-only flushing produced. SOmething like DS40 in a powerflusher does get things really clean, (and leaky!)
Old rads will release an awful lot of sludge if taken into the garden and inverted and hosed several times. Balance that effort against the lowish cost of a new set of rads though.

Taking out 2ndry hex's for a clean in acid is almost a "major service" item, which many combis benefit from after a few years. It usually doesn't take long, and it's much cheaper than a powerflush.

For a combi swap, if pre-soaking with chems isn't possible, I'll send the mains round each rad ( which shows the condition) until it's clear, and dose with x100 or simiilar. More than that is OTT on most systems, is my judgement so far.

Yes I'd agree, that powerflushing is often something of a con, unless you want to call it "being sure".

 

[sambotc]

One other point to consider is the hardness of water . In devon/cornwall the water is very soft and we have almost no problems with scale build up.

At a guess i would say that scale deposit's on internal's would cause a 'key' for sludge to stick to a lot easier which will contribute to the problem. Also boiler manufacturers will recommend anything they can which will help there parts last longer as it makes there boilers look more reliable. Actually the fact that the parts are being produced at a cheaper rate using inferior materials may be the cause to newer boiler failing more often.

Powerflushing has it's benefit's. As i said i own a powerflush unit and have seen the result's. My arguement was simply the fact that in my opinion powerflushing is a great way of adding a nice amount onto a job and giving the customer a sense of reassurance, and often it is not needed.

Sam

 

[nickso]

Nickso that is why on completion of a system you hot and cold flush using a chemical such as x300 and then inhibitor .

yes of course, but how many installers actually do it?

in my experience the combi swap is one of the worst culpirits for not being commissioned properly. too many installers seem to see clear water and just whack a combi in get the money and run.