Power flush or sludge?

[Richie866]

Hi guys, I'm biting the bullet and having my open vented system chahged to an unvented with a new boiler. The boiler is going to be a Vaillant 630 and the tank a Gledhill 250l. My plumber recomended this instead of the Vaillant tank - any advice if the Gledhill is any good? Also the main question, he said don't bother with a power flush. I'm to drain the system put some de-sludge in for a week and then he's going to do the work. Does this sound right? All the info I have read says to power flush. Ok its saving me a few bob but I want the set up to work as its costing me £4750. He says it will be just as good as he is fitting a magnclean in as well.

One last question - when the flow was checked I was getting 22l/min, although this was through a 15mm pipe. I've been told this will increase to 30l/min as the pipe is currently on a 22mm to 15mm reducer. When its straight through the 22mm pipe i'll get the 30l/min. Does this also sound right.

Many thanks in advance

 

[Richie866]

Any help would be greatly appreciated chaps, I really don't want to fork out all this dosh unless I'm certain my plumber is telling me the right stuff

 

[dextrous]

Well, he's the installer and he'll have to sign it off and fill the benchmark forms in. Out of idle curiousity, is he fitting new TRV's on the unspecified number of radiators of an undetermined age, which are piped up using a non-defined gauge of pipe? Also has your current system ever exhibited signs of sludge related problems, and has it had it's inhibitor levels topped up over the years?

Also, did he explain why he prefers to use the gledhill instead of unistor?

Finally, why do you doubt his word on the matter and how many quotes have you had?

 

[Richie866]

the rads are anything from 5 to 15 years old, all in good nick with trv's allready fitted. The pipe is all copper 15mm. No sludge problems to speak off but inhibator has not been topped up.

The reason I'm concerned is cause I'm spending a hell of a lot of money (for me anyway) and any boiler literature I've read says to warranty it the system needs a power flush before fitting.

The quote I'm going for is £220 dearer than the cheapest and £1000 cheaper than the dearest.

I have been told the Gledhill is just as good as the Unistore. As my knowledge of the product is not good any advice on the whole of the question would be greatly appreciated

 

[crockett]

I take it you've obtained more than one quote, and this quote is the one you prefer. If your chosen plumber has given you recommendations, then why not go with that? i know you're after a bit of 'backup', forewarned is forearmed and all that, but as Dextrous said, the guy's got to sign off on it all, change rad valves if required, etc. Have some faith in your choice my friend

 

[qplumb2010]

for warrenty purposes all thats required is a flush which he is doing, your going for a cheaper qoute so therefore getting less work, i know a lot of people who only hot flush a system, but i always prefer to powerflush especially where old rads are in place, but this can add 250-350 onto the price. i dont forsee any problems with a well maintained system like yours. so wouldnt worry too much about it.

the cyclinder is fine, so is the vailant.

 

[crockett]

Another issue with powerflushing, on older systems, is that the act of flushing can remove deposits that were sealing the odd pinhole here and there, or general weakness in the rads, etc. Not always the case, but it has happened.

 

[OvertonPlumber]

Ive power-flushed in excess of 500 systems and have never had a radiator collapse or leak as a consequence. Yes kamco fx2 is pretty nasty stuff but you would have to run through sulfuric, phosphoric or hydrochloric acid at very strong concentrations to actually melt metal.

 

[dextrous]

Ive power-flushed in excess of 500 systems

And that was just this morning

 

[Richie866]

Thaks for all your replies guys, and yes I was after reassurance. I'll sleep better tonight!

One last question (promise!) will the flow really increase from 22l/min to 30l/min when the 15mm t is removed and the system is fed by the 22mm pipe?

 

[crockett]

Indeed it will richie. As for powerflushing, Mr Benchmark, I have never had a rad collapse either, but I have had a rad leak on the seam after a powerflush, it was old, and further inspection quite rusty along its bottom edge. It is possible to aggravate and speed up a problem that may occur in the future, by powerflushing. You, in your 500 or so flushes haven't had this issue which is a good thing. I have done less than 50, on some quite old systems, and it has happened once. Just saying it can happen

 

[dextrous]

One last question (promise!) will the flow really increase from 22l/min to 30l/min when the 15mm t is removed and the system is fed by the 22mm pipe?

Not convinced - the increase from 7.5mm to 11mm radius will increase the cross section by an annulus of width 3.5mm, which is about 38.5 sq mm. This is a 21.2% increase in cross section, which would increase 22 up to 26.6 lpm.

However, this would assume that the incoming mains was providing water at a sufficient flow rate in the first place to permit this increase to take place.

 

[crockett]

Flow rate is the decider, Dex, yes

 

[dextrous]

Oh yes indeedy crock. There's a thought in my mind that suggests that since the current arrangement yields 22lpm, then this indicates that the incoming flow rate will enable the 26.6lpm to be achieved. On the other hand, I'm not entirely sure of my logic

 

[Richie866]

So guys do you reckon my money will be well spent, with plenty of flow for a decent shower?!!