Unvented cylinder descale...

[phazed]

Hey folks, first post, come to pick some brains!

I've had a problem with hot water flow for a while, which has slowly degraded to the point that it takes half hour to run a bath.

I have a Range Tribune HE Cylinder supplied by a standard gas boiler.
My house is only 4 years old, therefor so is the heating system.

Cold water pressure throughout the house is extremely good, however, as I've stated the hot pressure is rubbish. I open a hot tap, get a sudden rush of good pressure, then 15 seconds later, it coughs, splutters and dies to a trickle.

Had a local Central Heating firm come and service the system recently, and they told me (and showed me, I saw it with my own eyes!) that the cylinder is badly scaled up. Although it's only 4 years old, we live in an area that is renowned for EXTREMELY hard water, therefore it's of no surprise. the Inlet and Outlet on the Cylinder where scaled up so badly you could barely see them. The cold supply was tested up to the cylinder and was perfectly fine.

Being a fairly competent plumber, I'm considering Descaling the cylinder myself, but would appreciate a few pointers on what to use, and the best way to do it.

All advice gratefully received.
Many thanks in advance.

 

[Deleted member 105431]

Check the pressure reducing valve and the strainer within it first; scale is not the problem!

 

[Boilerman2]

Un-vented Systems should only be repaired by Engineers with a G3 Certificate, I assume the Engineer that investigated your fault is G3 competent? if so I assume he has cleaned the inlet strainer? (its in the Pressure Reducing Valve Group) if scale is such an issue in your area you would be well advised to fit a Water softener (not conditioner) it does sound like a problem with the PRV group/strainer though

 

[phazed]

Un-vented Systems should only be repaired by Engineers with a G3 Certificate, I assume the Engineer that investigated your fault is G3 competent? if so I assume he has cleaned the inlet strainer? (its in the Pressure Reducing Valve Group) if scale is such an issue in your area you would be well advised to fit a Water softener (not conditioner) it does sound like a problem with the PRV group/strainer though

Thanks for the replies Boilerman & dangermouse.....

With regard strainer, it's definately been checked twice, and it's clean.
The PRV, the engineer took it off, did a visual inspection, which he said looked ok, didn't appear to be sticking, but he didn't actually have another one at hand to test if that was the problem.

What he did say was, and forgive me If I've forgotten a few details, that the inlet was so scalled up that the bore of the pipe(?) was so small it was reducing the pressure to practically nothing.

So, when I first open a hot water tap, I get a sudden rush of hot pressure, where the pressure has built over time in the cylinder, then it drops to a trickle as the cold inlet simply cannot keep up with the demand as it's so scaled up.

The company I use are indeed reputable in my area. They actually have the contract for all of the local authority housing in my area, so they're quite big. The engineer is definately G3 ticketed, although he didn't seem to have a lot of knowledge of my cylinder.

The options I was given, were to get a new PRV assembly, but he didn't seem to think that was the problem. If it didn't solve the problem, I'd have to pay for that, and either Descaling the cylinder, or fitting a new cylinder!

A bit concerned I'm being taken for a layman here!!

EDIT. Yes, whatever the outcome, I'll be getting some kind of softening treatment installed. The water here really is rediculously hard.

 

[wetshoes]

Hi Phazed,
I'd put money on it being scale in the bottom of the cylinder.
I also live in a very hard water area & I've done loads of these.

If you have a balanced cold water take off and your flow from the cold taps is ok then that would pretty much prove it is scale & its not difficult to put right.

rgds

 

[kevindgas]

we do this on a regular basis in poole where scale is a major problem. we have a ferroli combi that scales in 12 months without fail, and an Ariston 210 litre unvented cylinder in another property that will only go 2 years before the problem returns.
the way we do it is to connect the cylinder to the powerflush machine using 2 washing machine hoses we then run fernox LS40 through the boiler / cylinder via the inlets /outlets. this takes around 20 mins on the boiler and an hour on the cylinder.

then cylinder is then drained and flushed twice to get the descaler out

 

[phazed]

Many thanks for all the replies guys.

Borrowed a power flush machine from a guy i know in the trade, ran fernox through the cylinder for about 3 hours, drained, repeat the process, flushed the cylinder a couple of times and voila! Back the the pressure I had when I first bought the house. Perfect

 

[kevindgas]

glad you are sorted !!

be careful not to drink the water as it can cause upset stomach if you didn't get all the LS out. and hot tank water is not good for you anyway!!

 

[heatingman]

last direct megaflow i cleaned, removed bottom stat and used wet/dry hoover, it was upto the boss hole in scale/calcium flakes. Hoover weighed tons. Lady was very concerned about using chemicals.