We’ve published a similar story here before, which is one of the reasons why our customer in this case study called us.

He recently bought a relatively new property (2011) with an Ideal iStor on the second floor, it wasn’t working properly, and he had been advised that it had been a money pit since virtually day one.

Our house, in the middle of our street. (Madness!).  Only it’s not our house, the owner is centre stage, just about to get the kettle on.

The other reason he got in contact with Hot Water & Central Heating Ltd was that he had used us for boiler installation before, in this case around 11 years ago (not in this house!).  A refreshing number of our early customers are using us again when they move house, I’m pleased to report.

The iStor is a one box solution incorporating an unvented water store and a boiler.  It’s quite a large floorstanding box, similar in size to a fridge freezer, and in the case of this model, one that was designed seemingly with little consideration to future maintenance.  Almost everything is difficult to get at, every repair or service job would be emotional.

The Ideal iStor, about to meet its maker.  The item to the right is a water filter, sad to say this made no appreciable improvement to the reliability.

We will publish another story of woe with a similar unit from another manufacturer, shortly.

In case you were wondering, the reason why many new build medium sized houses from the 1990s onwards were fitted with this type of ‘one box solution’ is simple.  Typically the boiler was constructed on a pallet; on arrival on site the pallet would be loaded onto a telehandler fork lift and posted into the requisite floor.  A team with basic plumbing abilities would then link it in with a few rolls of microbore plastic pipe to the radiators, and later on (hopefully) a gas registered fitter would make the final connection.  Job done, minimal time, maximum space utilisation, and a good performance hot water system, on paper at least.

The trouble is, they were usually designed using an off the shelf wall hung boiler, fitted into a bigger frame with everything else squeezed in around it.

Builders specifying this solution on new build estates weren’t overly worried what would happen 5 years down the line and thereafter.

Our brief to replace this unit, in the Caterham area of Surrey, wanted it to be easily maintainable, require minimal repairs over the lifetime, but to fit inside the existing cupboard and deliver a similar hot water performance to the iStor when it was new.

Viessmann WBIB Compact

There was a long flue run with limited clearances, which ruled out a Worcester Bosch boiler.  Instead we specified a Viessmann WB1B Compact 26Kw boiler, which we have been installing since 2006.  It is a refreshingly robust and simple design, and you can easily clean the heat exchanger internals annually – not something you might want to do with some other boiler designs.  Fully stainless steel, it is also impressively quiet, which is perfect for a bedroom cupboard.

it was tight, but ultimately achievable

We coupled this to a Fabdec 3S Venturi unvented cylinder.  As regular readers of our blog will know, this is our preferred unvented cylinder, because it uses a patented system to prevent the internal cylinder airgap from ever depleting, making it virtually maintenance free.

Fabdec have a capability that surpasses most other cylinder manufacturers;


Fabdec 3S Venturi device on inlet water supply

Tim; and his handiwork

The beauty of this pairing is that both items just fit into the cupboard, and both are reliable.  And if either does go wrong, they are simple to fix, and in any case come with very long warranties.  For instance, the Viessmann 100W boiler has a 10yr guarantee.

Tim and our happy customer