To flush or not to flush...

[Graham46]

…that is the question.

I've just refitted the family bathroom of our 19-year old Bovis house in the hard water area of Hertfordshire. The wife wanted a nice shiny chrome heated towel rail instead of the radiator. We got a cheap and cheerful Kudox one from B&Q which is now repositioned on the wall and I am all ready to get our regular plumber to come and extend the 10mm small bore pipes to reach it.

The instructions with the towel rail insist that: "the system MUST be thoroughly flushed with an industry approved CH cleanser. Following cleansing an industry approved CH protector MUST be added. Failure to cleanse and protect the system correctly is likely to cause small pinhole leaks and invalidate the guarantee…."

To save on time and charges I asked my plumber if I could cleanse the system myself before he does the work and asked him for a recommendation re the make of cleanser to use. He suggested Sentinel so I got X400 to cleanse and X100 as inhibitor.

The system is driven by a Baxi WM 38 3RS in the garage heating 10 radiators and hot water in a pressurised cylinder in the airing cupboard. The header tank is also set high in the airing cupboard. We have never flushed the CH system in 11 years and for certain the previous owners who had the house from new never did either.

I have had a peek into the header tank to see how to tie up the ball valve. There is a lot of "scum" on the water and a nice bright green trail of "slime" from the inlet valve down to the surface of the water. I lowered the ball valve to let some water in and the water in the tank started to "fizz" like undoing a bottle of fizzy drink.

Being naturally cautious I have stopped at that point. Can anyone tell me why the water in the header tank is fizzing when I add more water? Does this mean that the water is treated with an inhibitor already?

I am now dubious about flushing the system in case I cause more problems with an aging boiler, pump, radiators water cylinder etc. Nothing has ever broken (so far) so everything is original but we are aware of neighbours in similar houses having to replace leaking rads, hot water tanks, boilers etc.

I have flushed out the old radiator from the bathroom to see if there was a lot of black sludge and there was none. There was a little black water when I first removed it but not a lot.

Should I leave well enough alone or flush? Or leave it to the plumber to do after he has plumbed in the towel rail? On that basis, if it does all go pear-shaped at least I have the professional on site to fix things?

Any advice gratefully received.

Graham

 

[SortedPlumbing]

If are are sayin you feeder tank is full of sludge - when you drain heating down all that sludge is just going to clogg up your 10mm pipe!

If i were you i wouldnt bother flushing it out but eventually you prob will need a power flush.

 

[ChrisR]

A suggestion:
Bale out the muck in the header tank.
Put X400 in for a few weeks, say 4.
Do a mains flush - one rad at a time and always with an open end (see FAQ's) making sure the cylinder isn't "short circuiting" the flow.
Put in X100.


Or leave it to a plumber to do

 

[Fluffster]

A powerflush on a 10mm microbore system is not recommended.
Go with ChrisR advice.
Pete

 

[Graham46]

Thanks for your comments SortedPlumbing and ChrisR

As I said, this is a wonderful Bovis-built house and the header tank is on a shelf at the top of the airing cupboard. There is only about 4 inches from the top of the tank to the ceiling in the cupboard so I can't really see whether there is sludge in the bottom of the tank or not. All I can see is the "scum" floating on top of the water. My main concern first of all is why it fizzes when I add water from the inlet valve. It really foams and droplets jump out from the surface like when you pour a really fizzy drink. Is it possible that there is still some chemical inhibitor on there from 19 years ago? Or have we grown something nasty in there?

ChrisR
I read the FAQs earlier this evening. But could you just expand on "always with an open end" please? All the downstairs rads have a drain-off on the lockshield valve.

And what do you think about the warning from the Kudox installation instructions about developing pinholes?

Regards
Graham

 

[uknokianut]

Maybe you could use a wet/ dry hoover and suck out the F+E tank - sounds like its gone a bit mouldy.

 

[simond]

Ignore the Kudos rail instructions.

If there is any scum in the F&E this ironically is usually a by product of the chemical inhibitor.

Clean off the scum and then when you fit the towel warmer, if you need to drain down, dose it up again with Sentinel X100 or similar. It is worth redosing the inhibitor whatever when the job is finished.

As said before, microbore is incompatible with a powerflusher and in any case, if you have no sludge, you don't need one anyway.

 

[JohnD]

I have a feeling the bubbles you see when you push the float down may just be dissolved air from the high-pressure mains. If you fill a glass of water from the kitchen tap, does it at first look cloudy, and clear from the bottom up? this is dissolved air coming out (like when you pour a Guinness). It is even possible, depending on your pipework, that air has been rising up the pipe towards the float valve and collecting there. Or it might be that the water is getting aerated as it squirts out.

IMO it is always worth having a squint in the F&E, possibly with a torch and miror, to see if it has mud in it. This mud is very fine particles, usually of brown rust, which get stirred up when you refill the tank, and it does no good to let them wash down into the radiators. I like to bale out this mud and sponge the tank clean, but I am just a householder, if I was a pro and had to charge for my time I might not bother.

Again, as a householder, I have been very pleased with the ability of X400 to dislodge old black sediment from inside the radiators and boiler, and let it be washed round in the circulating water until either you drain it, or the X400 loses its power (some people say after 4 weeks) or you trap and remove the black sediment with a Magnaclean or similar (which is very satisfying).

 

[Graham46]

Thanks everyone for your further comments and suggestions

@JohnD
I just tried your water into a glass experiment and no, I only got a few big bubbles as the water hit the bottom of the glass which went in a couple of seconds leaving the water absolutely clear. I know exactly what you mean and have seen it elsewhere.

Thinking about it overnight I have come to the same conclusion as you. Torch and mirror to see what I can see in the tank. Rubber gloves and bale out the scum and water. Clean any sediment out with a sponge. Drain the whole system and see what comes out by flushing with just water. Then get the plumber to fit the rail. And as per the rail instructions apply the X400 for 4 weeks. Then drain and flush till water runs clear. Finally apply X100 inhibitor and hope we haven't found any pinholes in my existing rads in the meantime.

I'll start the dirty tank cleaning job tomorrow and see what comes out after 19 years. I'll let you know how I get on if you're interested.

Cheers
Graham

 

[JohnD]

that sounds great

if you can afford an extra £100 and do simple plumbing, fit a Magnaclean while you're drained. You will be amazed and gratified by how much it captures, and goes on doing it for months (though the amount will slowly reduce).

 

[Graham46]

@JohnD
Dead right. Lots of nice rust-brown "mud" in the bottom of the header tank all now baled and sponged. Lovely job with no headroom in the airing cupboard working blind or with torch and mirror! Then flushed all ground-floor rads with water only. This was amazingly clean: a light straw colour to start with (from the top of the rad I presume) then turning a bit grey as the rad emptied but not really much black sediment after all this time.

Re-bled all rads and tried the CH. All OK and is it my imagination or is the pump running more quietly? It could always be heard setting up a reverberation in the whole system before but not now.

Anyway, asked the plumber to come and re-pipe the heated towel rail. Then I will see what 4 weeks of X400 will shift in the way of black sludge. Looking forward to that!!

Thanks for your and others' help with this.

Cheers
Graham

 

[Agile]

10 mm microbore can be flushed fine IF the feeds to each rad are on opposite ends.

The limitation is when the rad is a double entry because the power flushing does not work well with the distribution tube which should be fitted inside.

Even 8 mm microbore can be power flushed but that much more often has the double entry valves.

Most 8 mm systems are pretty impossinle because most are 20-30 years old and well sludged up and even using citric acid just causes all the rad valves to leak in not many of the rads as well.

Tony

 

[JohnD]

when you put in the X400 remember to tie up the ballvalve and drain a couple of buckets of water out first, so the chemical is drawn down during refill.

I bet you will find the water soon goes black.

Can you afford a Magnaclean?

 

[gas4you]

Not what Sentinel teach on their powerflush training day.

Microbore generally will not give good results when powerflushed, as a gravity HW system will not either.

Powerflush = high flow, low pressure.

 

[Graham46]

@JohnD
I was wondering exactly how to introduce the X400. Is a "couple of bucketfuls" most of the water in the tank? I was thinking of just leaving a couple of inches in the bottom - say up to the "out" pipe level. Then add the cleanser, switch on the water again to help mix it up and also switch on the heating to get the pump circulating the mixture. Bleed the rads and let the X400 do its job. Will this sequence be OK or should I bleed the rads before switching on the pump?

Plumber confirmed coming first thing Monday.

Have a good weekend.

Cheers
Graham