Mains Pressure Unvented Systems

[Kevin Campbell]

Hi,

I am replacing my current 20 yr old HW cylinder and am considering installing a mains pressure unvented system to remove the need for a shower pump.

The installation instructions for some of these cylinders describe particular building regulations to follow etc. and it does not look overly complex but is the installation something that can be legally carried out by a proficient diyer or does it require a professional.

Looking at the supplier web sites there seems to be quite a variation in price between Thermasaver, Heatrae and Albion. Is there a significant difference between them or does anyone have particular experience of installing and commisioning them?

Thanks

Kevin

[Andy Hall]

There are two main options.

-You can use a BBA or Institute of Plumbing approved installer

- You can issue a Building Notice at your local authority. This will carry a fee which is based on the commercial (not DIY) cost of the works. Details from your local authority building control department. Be prepared for fun if you go this route, because the implementation of the legislation intends you to go for the first option.

If you know what you are doing, there is no specific reason why you shouldn't do the work provided that you use the correct components in the correct places. However, remember that you have potentially 200 litres of scalding water under pressure, so not unreasonably it's important that the installation is done safely. This is why there is a competent installer scheme and an alternative route if not.

Don't be tempted to skip this because you will find the house unsaleable if you don't have the paper trail.

.andy

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[IMM]

Kevin,

Unvented cylinders require a BBA approved fitter. Not a DIY task. A DHW only heat banks is superior in many aspects and can be DIYed. Some versions don't even require an overflow pipe to the outside. Unvented cylinders are at high pressure and require complex pressure reducing and control valves and kit. Heat banks are at low pressure and still give full mains pressure hot water.

Unvented cylinders require annual servicing. If one bursts (and when they go they go with abig insurance job) your insurance company may not pay out if it is not serviced each year, and certainly if not fitted by a BBA fitter.

See:

(go to thermal storage)

[Andy Hall]

There are a number of pitfalls for the unwary in this.

A Google search for previous threads on the limitations of this approach would be advisable

.andy

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[IMM]

Not of they follow what I outlined.

[David]

I was also under the impression that unvented cylinders required annual servicing; however when I recently had our unvented Vaillant system serviced (by an in-house Vaillant engineer) the guy did the boiler but didn't even want to look at the cylinder (see previous thread at

Other respondents seemed to indicate that was reasonable...??

David

[IMM]

David,

If you have the council signing it off and the BBA man signing it off to, then fine. If it requires an annual service then you have better get one done each year by a BBA man, otherwise the insurance company will not pay up.

[IMM]

David,

Check with Vaillant. Emphasise: service, insurance.

[IMM]

Please supply link to spurious information.

[Andy Hall]

No need. A search on your name plus keywords such as "combi" and "heatbank" will reveal about 90% of the spurious information generated in this NG.

.andy

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[IMM]

The topic was a combi boiler supplying the shower and a combi cylinder supplying the rest. Link please? I assume you made it up; about the Google and all that.

[Andy Hall]

Actually not. The topic was about a mains pressure unvented cylinder. You introduced combination boilers, tanks and underwear.....

.andy

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[IMM]

Actually yes.

The OP wanted a solution to a problem. I gave a far better and cheaper solution. One which you should have adopted, but you never knew.

You are cracking up man. Get professional attention.

[Phil Addison]

Qué ?? (1)

Phil Addison

1. Fawlty Towers, any episode you like.

-- Phil Addison The uk.d-i-y FAQ is at

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