New indirect unveted cylinder

[chrisalderman]

Hi,

Just about to replace my 3 year old cylinder. Thermostat failed and now the cold inlet is blocked due to scale.
I got two quotes till now. One for a Range Tribune HE 210L (same as the current one that needs replacing) and one for a RM StelFlow 210L, second a bit cheaper. Which one of these you guys recommend?

Cheers,
Chris

[chris watkins]

Chris, if you are having to replace your cylinder after 3 years then don't replace it with the same one. If this is a stainless steel un-vented one then I have never heard of one scaling up & if the thermostat has gone why cant it be replaced. Most of these s/steel tanks carry a 10 - 25 year (or even in some cases a lifetime) guarantee. It is far more likely that the poor water flow is to do with the control valve set than a blocked cold feed which could be de-scaled anyway.
Get a second opinion be fore you spend a lot of money.

[chrisalderman]

Thanks Chris. The thermostat failed and the water is really hot (way above 55C). That seems to cause the scale to build up much quicker then expected. I live in a hard water area. I had two plumbers that checked and one of them replaced the whole Inlet Control Set without any effect. I do have good pressure for cold water, so it seems it must be something inside the cylinder.

[Roger Welton]

Probably worth investing in a softener if the water is that hard.

Though I would get a second opinion, seems like madness to through away a unvented cylinder after just 3 years. Even if full of scale, just clear it out, sometimes the outlet on the top can become restricted with scale that needs clearing.

[chris watkins]

Even so, cylinder can be descaled. Unless they leak I have never had to replace a s/steel unit & we work on these all the time it is almost a specialist area, so I do know what I am talking about but if you want a new one go with a Megaflo if you can afford it & a Potterton gold if you can't.
I would still get a second opinion if I were you. where about's are you??

[chris watkins]

By the way 60 -65 degC is normal & no less than 55degC. You should not need any form of softening for the HW cylinder unless for other reasons.

[chrisalderman]

I'm living in North Hampshire. When I open the hot water, I get good pressure for about 20 secs, then drops. The top outlet is clear, very clear. Scale was found only on the cold inlet, inside cylinder. Apparently inside the cylinder the cold inlet has a bend and the assumption is that that bend is blocked. All pipes were checked, in an out, and all clear (it's a new build so all pipes are new). Also one thing we tried is to drain the cylinder and refill. Refill took more than 1h. The pressure dropped quite fast, in about 1 month, so I was very confused about explanations. But, two plumbers came with same conclusion, so I start thinking that instead of spending soon same amount of money to investigate the problem, better just replace it.
The descale idea sounds interesting Chris. Is it time consuming, expensive?

[tamz]

Has anyone checked the filter on the combination valve?

[chris watkins]

No, not when we do it but from what you have just posted, it is not scale, if not as tamz say the filter in the control valve set cos you have had it replaced then it is further down or along the pipe. Has anybody checked the flow rate through the pipe ? Do you know if you have balanced cold water?
Can you post a photo or two of the cylinder pipework / control valve set ?

[chrisalderman]

Few pictures below.

First is the cylinder with all the bits.
Cylinder.jpg

This is the Inlet Control Set, it was replaced completely. It did not solved anything. It is a balanced cold water and the cold water pressure is very good.
InletControlSet.jpg
The cold inlet, the arrow, is where the scale was found, not on the external pipe, but inside the cylinder. The pipe is hot, I can keep my hands on it few secs. It's cold near the inlet control set.
ColdInlet.jpg

Thanks,
Chris

[Roger Welton]

If you disconnect the fill loop from the heating system and run it into a bucket what is the flow like?

[BLOD]

It looks like you've got a balanced take off for the cold water from the inlet control set, so if you're cold water is working ok then the control set is unlikely to be the problem.

Ive descaled loads of these, although usually direct models are the worst.
the scale sits in a big mound over the inlet at the bottom of the cylinder.
The symptoms are as you say - good pressure for a short while then flow goes almost down to a dribble in some cases.
Do you use you're electric immersion at all ?

[BLOD]

Forgot to say - Imo I'd try to descale it and then fit some sort of limescale prevention device.
A new unvented cylinder every 3 years is not the way to go !

[AWheating]

if its a 3 year old new build and the manufactures instructions require a scale prevention device on the inlet of the cylinder then you should be able to get it fixed free of charge under your house builders 10year warantee provider. It is a laten defect which means a design fault/fault that has occurred due to incorrect installation and not ware and tear and as such should be covered even if the original plumbers warantee period is over.

[mountainman]

I agree with AW.