Megaflo scale problems - advice required on descale.

[Dave_79]

Fair point chaps. Water temp at the tap was only 45 degrees this morning so I've nudged the stat back up to around 65 on the tank and 70 on the boiler. Boiler ran for 20 mins then when it stopped I ran the kitchen tap for about 10 seconds before the familiar gurgling happened. Before this I hadn't had a major deposit for a few days, just the odd flake.

Sat them in pure oust for 10 mins - not even the slightest fizzing or hint at dissolving. Added boiling water, still nothing. Consistency is solid but soft. Can grind this to dust/sludge in my fingers with little pressure.

 

[Dave_79]

It's just constant now - kitchen hot tap gargling and banging whenever it's run. Mesh filter is off as it clogs within 1 second. Just filled a vase...

 

[Gasguru]

Have you tried drying the "scale" first and then seeing if it's combustable...perhaps the baffle is disintagrating.

 

[Dave_79]

Hi Gasguru. I hadn't tried that, but I just held a lighter directly to a small piece and it turned to a yellowish liquid, then immediately back to solid once the flame was removed. Definitely not combustable.

The tap appears to have cleared itself for now. Obviously the increased heat in the boiler/tank caused a load to dislodge and now that's come out it's running clear (with the boiler off). Water temp at tap 60 degrees.

I still think it deposits mainly when the boiler is running or has recently run.

 

[muggles]

https://www.socotec.co.uk/services/laboratory-and-analytical-services/

I think it's worth getting a sample analysed

 

[Lower]

That can't be scale. It looks like something inside the tank is breaking down. I presume there is no sign of anything in the cold water supply, ie nothing is coming into the house water system from outside.

 

[MeldrewsMate]

You've had good advice so far:
1. Analyse a sample, then you can work out where it comes from or how it forms, then take the correct steps to eliminate it.
2. Fit a strainer to the hot water outlet pipe to prevent blocked taps...it looks like a large boddied one will be needed or you'll be clearing it every day, but a coarse strainer should suffice.
3. Write down the facts. You've got useful information wrt when it occurs and when it doesn't occur. Once you've a plan to resolve the problem make sure that the solution will resolve all of the symptoms, or it's not going to fully work.

Finally, if you are going to have the tank chemically cleaned, have the plumber vacuum out as much debris/scale/smeg as possible through the immersion heater hole, this way you'll use much less expensive chemical and you'll get to inspect the condition of the (unused) immersion element.
PS Citric acid is much cheaper than Fernox descaler, and it won't seem to 'linger' in the distribution pipework for as long as DS3.

 

[Dave_79]

That's correct Lower. Just from the hot outlets feeding from the tank.

I hadn't considered anything other than normal scale. I'm just sat here reading about debris from a disintegrated "water heater dip tube" but whatever that is (?) it seems an old issue.

https://inspectapedia.com/plumbing/Hot_Water_Tank_Debris_Flush.php

End of the day I've no idea what was inside this tank when the house was built. Given some of the other 'surprises' I've found over the years it wouldn't shock me if the builders have chucked their lunch away inside it!

Will give the tank another flush asap and make sure the air bubble is ok, then maybe run the immersion for a few hours to see if that dislodges anything. Then I'll get a plumber to come and remove/replace the immersion element and try and get a view inside the tank. In the meantime, increasing the water temp seems to have made a load shoot out and then clear up... but that could just be the currents in the tank shifting stuff around.

Cheers

 

[snb]

i have a few on private water supplies that scale up very quickly. Have drained down cylinders to find that the bottom 300mm is virtually all scale and that has happened within a year. on a mains connected system you would expect 6 to 10 years but wit the right conditions this can be much quicker.

Most likely to be scale formed on the coil within the cylinder and since the heating has been on has caused a few slugs of very hot system water water to be sent through the hot water coil causing the scale to be broken off due to thermal expansion.

Get the cylinder serviced but main make sure they clean the scale out. we usually hoover most out through the immersion outlet, and then add citric acid to clean the remainder.

 

[Dave_79]

snb - Thanks for your input, I've read similar online to your comments and to me it still looks like scale, and seems to come loose when the water is hotter. Will definitely get it vac'd out. But is it the main coil or the immersion that tends to scale... or both?

And if it is scale, why doesn't Oust dissolve the chunks being left in the taps?

Cheers.

 

[snb]

the scale is formed on both the immersion element and the main coil if the conditions are right. normally the immersion coil temp causes the formation to be smaller fine particles that fall off to the bottom of the cylinder where they can form together.
If the main heating coil is much above 70c ( which is why we generally leave them set on 70c) then the main coil will form scale on it but this will be much larger often way too big to even leave the cylinder by the tap route and can only be hoover out. ( sometimes they are so large and hard it is not possible to remove them.

The reason why oust will not dissolve some chunks is due to the make up of the scale. Try a little citric acid or vinegar. I'm fairly certain all of what you have is due to the temps at which your cylinder has been heating at over the last few years

 

[Dave_79]

Just an update. I got some Citric acid crystals and added it with boiling water to the 'scale' I'd collected. Didn't do anything.



I descaled the kettle to test and the citric acid worked wonders (better than Oust). So I added the 'scale' into the kettle and boiled it up with Citric Acid - still nothing. Vinegar also doesn't work. So definitely leaning to it not being scale. Will send a sample off when I collect some more.

I'm wondering if there could be something in the internal expansion vessel breaking down. I seem to have to recharge it quite often. It's supposed to take 2 mins to stop gurgling but this time it was still giving out glugs after an hour with the TPR valve open. In the end I had to open the 8 bar pressure valve to let a bit of water out, then it eventually stopped.

 

[snb]

the internal baffle plate is made of a white plastic. when you recharge the air bubble you should open a couple of hot taps and the tprv. It normally takes up to 10 mins to recharge (noise to stop). The pieces of plastic look very much like resin out of a failed water softener.

 

[2Jays]

Got virtually the same problem here with Megaflo, taps blocking up more and more frequently with stuff that isn't affected by normal scale cleaners, doesn't fizz in vinegar. Plumber suggested fitting a "Scalemaster" to cold water inlet, not convinced about that at all. Would getting a strainer fitted affect the water pressure in the shower?

 

[dilalio]

I'd give megaflo a call and ask their thoughts on it. It may be a known issue with air bubble components inside the cylinder reacting with the water.

As dilalio says it could be the plastic ring that makes the bubble breaking down.