Mains water Non Return Valve

Hi,

Currently intalling a completely new central heating system, bathroom, hot water supply, etc. Using an deal Isar 30 combi boiler. It's an old house and what little there was before has all been stripped out.

The sealed heating system will have its own non return valve to stop contamination.

My questions is regarding the need and/or requirement for a non return valve on the cold water mains supply.

The boiler manual mentions adding one if connecting to a shower, but also states that if you do so, you must allow for any expansion of water contained.

Any advice or comments would be much appreciated.

Robin

The only non return valves required in a hot or cold water distribution system is at the outlets.

Mixer showers always need them but they are sometimes built in.

Fitting them anywhere else can cause problems.

I hope you are CORGI.

Tony

The shower being installed does contain an integral non return valve.
I was only confused as part of the manual briefly mentioned the use of one on the cold water inlet to the boiler when used with a shower.
http://www.idealboilers.com/docs/pdf/isar_he_manual.pdf
Page 11, part 4.a. I couldn't make sense as to how a non-return valve at the boiler would make a difference.

Thanks for your help.
Robin

P.S. No I am not CORGI, this was a question regarding water plumbing.

Para 4a on Page 11 is about the boiler filling system or filling loop as would normally be fitted.

I dont know why you thought this is a water plumbing aspect. It is associated with installing the boiler.

If you are really installing the boiler then I hoped that you were CORGI registered.

If you are not installing the boiler then I wonder why you are looking at the boiler's MI.

As you started off by saying

"""Currently installing a completely new central heating system, bathroom, hot water supply, etc. using an Ideal Isar 30 combi boiler"""

Then obviously I thought that you were doing what you had said!



Tony

DOMESTIC HOT WATER
4. When connecting to suitable showers, ensure that:
a. The cold inlet to the boiler is fitted with an approved
anti-vacuum or syphon non-return valve.

The section at the top of page 11 related to the central heating. The part I was referring to is about Domestic Hot Water.

I still do not understand why there would be a need for a non-return valve at the cold inlet to the boiler.

At present, there is no gas in the house and I am installing all of the radiators, showers, taps and water pipes into the boilers piping frame.

The manual contains a lot of information that it would be stupid to ignore when installing the rest of the system. It is always advisable to know as much as you can whoever is installing it.

I have not relooked at the MI but I think what they are doing is to prevent a situation arising where they could be blamed for a breach of Water Regs.

Showers and many other outlets DO need a non return valve but these should always be fitted at the outlet.

A non return should normally NEVER be fitted before a boiler as they are not required. If for any special reason one was fitted then there MUST be an expansion vessel fitted on the DHW output to absorb expansion.

Tony

Agile said:

If you are really installing the boiler then I hoped that you were CORGI registered.

Click to expand...

Why should he be CORGI registered. This is a DIY forum and gas work can be legally DIYed.

On CORGI's web site in the section on achieving ACS Accreditation.

" Until 1998, gas installers could achieve certificates of competence through a number of different certification schemes - resulting in an inconsistency of standards across the UK. Those separate schemes have now been replaced by the Nationally Accredited Certification Scheme for Individual Gas Fitting Operatives (ACS).

This means that all operatives are assessed within nationally agreed standards, to gain certificates that need renewal every five years. Assessments are available from some 150 centres around the UK. Each of these has been approved by one of six certification bodies accredited by the United Kingdom Accreditation Service (UKAS)."

'All gas installation businesses and operatives must be in a "class of persons" approved by the Health and Safety Executive. That currently means they must be registered with CORGI.'

This does not apply to DIY work. CORGI, as expected, say “could be dangerous" and "likely to be illegal". Bullshit words.

Here is the referring Statutory Instrument.
http://www.hmso.gov.uk/si/si1998/19982451.htm

The HSE published a complete Fundamental Review of Gas Safety

http://www.hse.gov.uk/gas/index.htm

In which there is a section discussing DIY

http://www.hse.gov.uk/fundgas.htm

It does say:

DIY installation and maintenance Question 30. Should DIY work be legally prohibited, e.g. by restricting the sale of gas equipment to registered gas installers? Should retailers be legally required to record sales of gas equipment and pass these to a central body, perhaps CORGI? Should any central body selected for this purpose be required to arrange the inspection of gas installation work in any case where the record of sale suggests work will be carried out by an unregistered installer? Should increased publicity on the dangers of DIY gas work be given by (i) HSE campaigns, (ii) manufacturer's warnings, (iii) other means? (HSC Discussion Document 'Gas Safety Review: option for change', DDE14a, Page 50) Recommendation 26

226. We understand concern about the possible risks posed by incompetent DIY gas work, but believe at present there is insufficient hard evidence of incidents to support the introduction of a legal ban. However, we recognise that current statistics might not tell the full story and recommend that further work be done more accurately to identify the scale of the problem, i.e. by refining arrangements for reporting incidents specifically to identify those related to DIY (see Recommendation 9), with a view to reviewing the legal position again (say in five years time).

227. In the meantime, we recommend that increased publicity should be given to the dangers of DIY gas work (possibly funded through industry and the Gas Safety Levy - see Recommendations 7 and 11). This should focus more on legal requirements for competence if DIY is undertaken, and penalties if these are not met. More encouragement should also be given to retailers for providing 'point of sale' information, and equipment manufacturers to include warnings with products.

Analysis of responses

228. Of a total 109 responses to Q 30, 54 supported the principle of banning DIY with 35 specifically against; whereas 44 were in favour of a ban in practice with 47 against (NB some voted just for principle or practice,
others for both). The similar question in the consumer document resulted in 29 favouring a ban with 31 against and 1 unclear. Replies to the public questionnaire showed 285 in favour of a ban with 54 against. The issue was also posted on a DIY Internet web site which provoked a number of responses from those practising DIY gas work; these were against more legal controls but generally supported further publicity, stressing competence requirements for DIY rather than frightening people away from doing it.

Argument

232. Data currently available suggests that a number of gas incidents have occurred over recent years where DIY is directly or indirectly implicated, but, the link is not always entirely clear and in some cases it is possible for other factors to have contributed. At present we do not believe that this evidence is sufficiently strong to suggest that current legal controls (ie for competence under GSIUR regulation 3(1)) are inadequate, and an absolute ban needs to be placed on DIY. If you look at some of the rest of the report, and contributing consultants reports concerning dangers in the home in general, you will read that in the gas arena, CO poisoning is by far and away the biggest issue, and that all gas related accidents in the home are a tiny proportion of the total.

DIY gas work is not illegal despite what CORGI men say. It is not a major concern of the HSE. That is clear.

This post should clear up all the unnecessary tripe posts on this topic. Just refer to this post the next time this topic arises.

I am totally for there being standards and safety measures in place to stop your average Joe from putting himself and others at risk. Gas being a prime example of this. Whether this should be controlled by CORGI is a different matter and could be debated till the cows come home.

What I dislike though, is completely unproductive comments that are irrelevant and do nothing but cloud over any answer to the question being asked.

Saying that, I have yet to find an explanation as to the paragraph in the manual that I mentioned.

Robin

Robin, I read that you are asking whether it is necessary to have a non;return valve in the cold feed to the combi boiler's DHW system. Water Regs say action must be taken to prevent contamination of the supply. In this case the expansion of heated water would cause the cold mains to back-flow, if only by a small amount. The normal solution is to fit a single check valve in the mains inlet, just after the stopcock, with the drain-point immediately after.
As far as expansion is concerned, none is required if the hot water storage capacity is less than 15 litres and there is adequate pipework volume in which to allow the expansion (sorry, I can't remember the exact figures and the footie is on).
This is nothing to do with the double check valve required between the central heating system water and the cold mains top-up (filling loop).

Hope this helps.

Bloody Ronaldo, hope Rooney decks him first day back, that's if the scumbag isn't too scared to turn up.

The technical author of the manual has caused confusion. What he should have said was "All potable water pipework and fittings must comply with all relevant standards including the current Water Supply (water fittings) regulations.

The regulations then cover in more detail the risk of backflow from shower hoses and other outlets - Showers normally require double check valves on the hot and cold or single check valves if the shower head can't be dipped into the tray/bath etc by a "bylaw" ring.

The anti-vacuum or syphon non-return valve appears to be the authors solution although as Tony points out the check valves are fitted on the supply pipework at the outlet.

Some manufacturers (and Ideal) insist in their manuals that if a check valve is fitted on the inlet to the boiler to prevent backflow of hot water into the supply pipe it should be accompanied by an expansion vessel after the check valve to accommodate the slight increased volume of the hot water.

I suggest you don't fit this valve. If you have high water pressure (say > 5bar) a mini expansion vessel may be warranted since the pressure could rise above the maximum limit of 10 bar.

Remember expanded water may be prevented from expanding back down the inlet pipe by the loose jumper in the incoming stopcock.

In truth many manuals are cobbled together and often contain ambiguity. Go by the water regulations guide since the boilers will have gone through a WRAS assessment.

The filling loop connected between the cold inlet and return pipe must have a double check valve on the COLD side. Filling loops are frequently connected with the double check valve on the heating side. This is not compliant and is done due to cheap loops only having one isolating valve and not two.

The filling loop should ALWAYS be disconnect after initial charge or top up if you want to comply with the Water Reg's