DFS 11 - DWR Cymru

(Saesneg yn unig)

Dwr Cymru Welsh Water is most grateful to be invited by Huw Lewis AM in his letter dated 19 March 2008 to submit evidence to his Committee relating to fire sprinkler systems in new residential premises.

It is emphasized that Dwr Cymru Welsh Water is waiting for the completion of national debates on policies and specifications and the subsequent recommendations by Water UK and the Water Regulations Advisory Scheme (WRAS) before producing its own final policy. Hence the information below incorporates our understanding of the current position of these debates and our thoughts on the way forward.

With particular reference to the three questions in his letter we would comment as follows:-

We do not feel that it is appropriate for this company to comment on Question 1

We consider that Matter 11.1 needs greater definition.

“a sprinkler system”. It should be defined as a sprinkler system designed to comply at all times of the day and year with BS 9251:2005; any subsequent amendments or equivalent superseding British Standard and any other relevant British Standard; and the design should also take into account expected changes that might prejudice compliance. (see notes below on pressure management development which supports the italics)

“new residential premises”. This needs clear definition to avoid confusion. Does it include everywhere people reside temporarily or permanently eg hotels; guest houses; hostels; university halls of residence; prisons? Does it include the whole of a building if only part of it is used as a residence eg a public house where the landlord’s family lives on the premise and a shop with a flat above. Does it include mobile homes (many of which are merely prefabricated homes without wheels)? Does it apply to the many rural premises that will only have a private source of water supply, often with little pressure and flow?

The definitions given in Matter 11.1 in sections (b),(c) and (d) are vital to understanding the intended meaning of “new residential premises” and “sprinkler systems” but as stated in (2) above they need further expansion to avoid confusion.

In drafting the order the Committee need to be aware of a number of matters which will need to be specified and a number of technical challenges that will frequently be encountered when designing sprinkler installations and the significant costs that may result in order to deal with them. The following evidence is an effort to summarize those challenges for the benefit of the Committee.

First of all Dwr Cymru Welsh Water accepts that the installation of fire sprinkler systems in residential premises on a large scale will result in the reduction in deaths due to fires at those premises and wants to give all the support it can to their installation. However the costs of providing a water supply with the necessary flow and pressure at each sprinkler head, additional to those for the domestic supply, should not be underestimated, and it is recommended that detailed studies of those costs should be carried out and considered before legislation is approved. It appears likely to this company that there will be a large number of properties where these costs could be significantly higher than the costs included in paragraph 32 of the Explanatory Memorandum.

The Committee will no doubt be aware that BS 9251: 2005 “Sprinkler Systems for Residential and Domestic Occupancies Code of Practice has separate definitions for Residential and Domestic occupancies and it is assumed that the order relates to both of these.

Specification Standard

We would hope and expect compliance with BS 9251:2005. This is a requirement of the draft Terms and Conditions issued by Water UK as a template for water undertakers to prepare their own Terms & Conditions.

A design compliant with BS 9251:2005 would be expected to be compliant at all times of the day and year and even take into account expected changes that might prejudice compliance. This needs to be clearly stated in the Order since some existing and proposed sprinkler systems are less resilient. It is our concern that our company, and possibly the Assembly, would be accused of negligence in allowing such an installation, particularly if an occupier died in a fire during a period of time that a sprinkler system was designed not to function properly.

Availability of Water

The Water Industry Act 1991 defines a supply for a sprinkler system to be a “supply for non-domestic purposes”. Such a supply is given on such terms as the water undertaker may agree with the applicant. The Act prevents the supply being given if in doing so it would put at risk the water undertaker’s ability to meet all its existing obligations to supply water and its probable future obligations to supply water for domestic purposes. In this event it is likely that mitigating works could be carried out but the costs, which could be prohibitively expensive, would need to be paid by the applicant and there could be a considerable delay to the supply being made available. In such a situation the use of storage instead of a direct supply is likely to be the optimum solution.

Whilst the water company would make no charge for any water used during a fire or for testing purposes it seems likely that an annual charge would need to be levied on the customer for maintenance and management of the water company apparatus relating to the sprinkler.

It is not expected that there will normally be any problem supplying a domestic premise with the necessary flow of 109 litres/minute (l/min) unless the existing or planned water main is only 50mm bore, but these are very few in number. The necessary flow of 218 l/min to residential premises will present a more frequent problem which might result in a proposed main and some existing mains being upsized, which might be very expensive. The relevant costs would need to be charged to the water supply applicant and there may be a delay in making the water supply available. These costs could however be avoided if storage was provided at the premise that could be filled slowly.

Whilst it might be possible to supply 109 and 218 l/min to a premise it needs to be appreciated that this would have a significant effect on the construction work to make the new connection, particularly when connections are being made to existing mains. The current standard connection to a single dwelling is with a 20mm bore pipe which can be made quite quickly without shutting down the main. In order to take 109 l/min from the main with manageable pressure losses it is likely that a 41 mm bore pipe and connection to the main will be needed, involving a shut down on some diameters and types of main. This will greatly increase the cost of a house connection, particularly if a water main shutdown is required and work will take longer resulting in longer disruption of road traffic. If water supply shut off’s become a common occurrence this will not be popular with customers. A residential premise requiring 218 l/min will probably require a 52mm bore pipe which will be even more expensive.

Pressure Availability

When unmanaged, the pressure in a water main can vary considerably in a 24 hour period; from season to season and when short, but possibly infrequent, high abstractions are taken from the main nearby. The Water Industry Act 1991 requires that water supplied for domestic purposes should merely have sufficient pressure to reach the top storey of the premise. The Regulator (ofwat) additionally requires that water undertakers report the number of properties that are likely to receive pressures below 1 bar (10 metres) with a flow of 9 litres/min. This is the pressure most water undertakers aim for in order to maximize efficiency and therefore will govern the pressure at the non-domestic (sprinkler system) supply point. It will be noted that this is well below the 3.5 bar (35m) that Dwr Cymru Welsh Water consider will be necessary to operate a sprinkler system without a pressure boosting pump.

However there are many kilometres of water main, particularly in hilly areas where the pressure is and always will be, greater than 3.5 bar and a pump would not be necessary for an efficiently designed sprinkler system.

But there are also many kilometres which for most of the time have in excess of 3.5 bar but for perhaps one or two hours each day, at peak demand times, the pressure will reduce to a lower value, often less than 2 bar. Many of these and other mains will have longer and even lower pressures in drought periods.

In order to make the supply of water more efficient by reducing leakage and general consumption, pressure management is extensively applied across our distribution systems. Pressure in these mains is managed to generally between 15 and 25 metres head; which will require a pump to be fitted to most sprinkler systems in those areas. This has greatly contributed to Dwr Cymru Welsh Water (DCWW) reducing its leakage by 50% since 1995. Pressure management will continue to spread over an increasing length of mains.

Water Meter

• A key component of the 3.5bar pressure that will be needed is due to a pressure loss of approximately 1bar (10 m) because of the need to fit a small diameter water meter on the sprinkler supply pipe. Though no charge can be made for water used for fire fighting purposes or for testing the apparatus, DCWW needs to fit a water meter to detect any leakage or theft of water. An appropriately sized meter (15mm) would not allow the necessary flows to the sprinkler systems but it is hoped that a 20mm meter would be an acceptable compromise. A 20mm meter will not detect such low flows as a 15mm meter but investigations will be carried out in the hope that the low flows detected by the 20mm meter will adequate. This would hopefully avoid the need to install an adequately sized storage tank (840 litres for a domestic premise and 5040 litres for a residential premise) which could be fed slowly from the domestic supply pipe before being pumped from the tank into the sprinkler system.

Maintenance

• It is extremely important that any pump and the sprinkler system are regularly maintained if they are to work properly when needed and are kept completely isolated from the potable supply system. As water within the sprinkler plumbing may never be used it will become stagnant and deteriorate and could give rise to serious ill health if cross connected to the potable supply system or if the necessary backflow prevention devices malfunction. Serious consideration needs to be given how to ensure that this maintenance will be carried out regularly by householders who cannot afford or understand the importance of maintenance.

Keith G Pratley

For Dwr Cymru Welsh Water

Notes to accompany the oral evidence of K G Pratley on 29 April 2008

Keith G Pratley, BSc Honours (Manchester), CEng, MICE, MCIWEM
Water Regulations & Water Efficiency Manager
Dwr Cymru Welsh Water

Credentials

I am a chartered civil engineer with 38 years experience as an engineer in the water industry. I have been a leading member of the water industry assisting with the preparation of specifications for domestic fire sprinkler systems since the water industry was invited to get involved in 2001.

I currently chair the Water Regulations Advisory Scheme (WRAS) Domestic Fire Sprinkler Committee formed to review the specification and policy matters relating to Domestic Fire Sprinklers in the UK (due to differences throughout the UK water industry). I am also a delegate for Water UK on the Sprinkler Co-ordination Group of stakeholders which was recently re-convened to debate the same issues. In addition I am also one of a small WRAS and Water UK delegation commenting on research done for the Department of Communities and Local Government CLG Department to prepare a specification for the Integrated Domestic Plumbing and Fire Sprinkler (IDP&FS) system (previously known as the Low Cost Fire Sprinkler System).

Evidence

The statements made below and the evidence given is my own which takes into account the views and comments made by members of the above working groups, and are not necessarily the views of Dwr Cymru Welsh Water (DCWW) which has yet to consider all the matters and confirm policies relating to domestic and residential fire sprinkler systems. A DCWW policy is unlikely to be published until the British Water Industry has agreed a national policy which will hopefully minimise the differences between the policies of the many water undertakers.

The British Water Industry is convinced that the installation of domestic and residential fire sprinkler systems on a large scale will result in a reduction in deaths due to fires at those premises and wants to give appropriate support to their installation. It is however extremely concerned to ensure that the supply of water that is given fulfils the expectations of the occupiers, stakeholders and society. In order to do this a number of issues need to be resolved and the solutions/decisions properly communicated to all stakeholders.

Issues

Controlling Specification

The installation of sprinkler domestic and residential sprinkler systems (hereafter merely referred to as “domestic”) is guided by BS 9251:2005 “Sprinkler systems for residential and domestic occupancies – Code of Practice”. Draft terms and conditions prepared by Water UK for the use of water undertakers state that a system complying with BS 9251 should be a condition of giving a supply.

The Water Industry would expect and hope that the Domestic Fire Safety LCO Committee will decide that compliance with BS 9251 will be a requirement of the Order.

Flow

Flow required by sprinklers

BS 9251 requires a domestic sprinkler system be designed to receive a minimum of 42 litres/min (l/min) to each of two sprinkler heads and a further 25 l/min for domestic use at the same time (Total= 109 l/min).

The Standard requires a residential sprinkler system to receive a minimum of 42 l/min to four sprinkler heads plus a further 50 l/min for domestic use (Total= 218 l/min).

Flow available

It is not expected there will normally be any problem supplying a premise with 109 l/min from water mains. However 50mm bore water mains often laid where few houses are connected off a short length of main would generally be too small. Flows of 218 l/min for residential sprinkler systems may require larger than normal sized mains to be laid. The extra costs of upsizing will need to be passed on to the property or site developer. The extra cost of slightly upsizing a planned new main would not be considerable, but costs will be considerable if an existing main also needs to be upsized. The committee should note that a new dwelling alongside an existing road that would receive its water supply from an existing main is likely to present more technical problems and be potentially more expensive than an estate of new houses which require a new system of water mains. Where the cost of supplying the high sprinkler flows is great the provision of storage will undoubtedly be the most economic solution.

Hydraulic considerations

Pipework configurations for sprinkler systems are included in BS 9251:2005.

When there is a flow of water to sprinkler heads there is a step by step reduction in water pressure all the way from the water main to each head. The pressure losses depend upon the amount of disturbance to smooth flow, the flow rate and the pipework/fitting diameters. The pressure losses will occur at:-

The abrupt exit from the main

The single check valve, included to prevent backflow

The water meter

System controller (which activates an alarm)

Each pipe elbow, tee and taper

Throughout the full length of the service pipe and by an amount dependent on the length, diameter and flow in each pipe section.

The Water Meter

All new premises are fitted with a water meter which needs to be kept as small as possible in order to measure the lowest possible flows to primarily minimise the amount of unaccounted for water (commonly known as “leakage” or “waste”). A 15mm meter is normally fitted to domestic premises to achieve this but its maximum flow rate is significantly less than the flow of 84 litres/min needed for a domestic sprinkler system. One solution is to fill an 840 litre (10 minutes supply) tank slowly from a standard domestic supply pipe (directly or indirectly) and then pump water from the tank to the sprinkler system. This has the great advantage that there would be no concern about any limitations to the water main pressure or flow and a standard domestic  connection and standard supply pipe can be laid.

An alternative solution would be a second direct supply to the sprinkler system. In order to minimise the installation costs for house-owners contemplating a sprinkler system and thereby encourage their installation, the Water UK council recommended to water companies that they do not fit a meter to the sprinkler supply. In making this recommendation the council undoubtedly did not consider the much higher risk of water theft and unknown leakage due to sprinklers being a standard feature of construction on a massive scale and therefore it is expected that Dwr Cymru Welsh Water would require meters to be fitted if sprinkler installation was mandatory for all new dwellings.

A 20mm meter would pass the sprinkler flow of 84 litres/min, albeit with a pressure loss of about 10 metres. This meter would hopefully detect, though not accurately measure, sufficiently small flows into the sprinkler system to allow leakage or theft to be identified. Studies need to be carried out to determine whether this would be satisfactory.

Pressure

Supply Pressure required by sprinklers

In order to work satisfactorily BS 9251 states that the water pressure at each sprinkler head must be 0.5 bar (approx. 5 metres water pressure). Pressure is lost in the water whilst passing through the pipes and fittings from the water company main to the sprinkler head. The pressure loss depends upon the flow rate, the distance and size of the pipes and fittings and will normally total at least 10 metres head, even with an economical design, plus a further 10 metres would be lost passing through a 20mm water meter. To this must be added the height of the highest sprinkler head above the water main (8 metres [say] for a two floor house and loft space). This gives a minimum total of 35 metres (3.5 bar) pressure that will be needed in the water main, plus any height the property might be above the road in which the main is laid.

Supply Pressure available

i)It should be appreciated that all water companies are expected by the regulator (ofwat) and its customers to operate as efficiently as possible. Steps are therefore being taken at all times to reduce waste of water by the company and customers by reducing pressures to as close as possible to the statutory and regulatory requirements.

ii) The Water Industry Act 1991 requires that water supplied for domestic purposes should merely have sufficient pressure to be able to reach the top storey of the house. Hence this minimum requirement would not have the additional 0.5 bar (5 metres) pressure needed to operate the sprinkler heads off the roof ridge beam, on the top storey ceiling or even possibly on the ceiling of the floor below the top storey.

iii) The Regulator (ofwat) requires that companies report on the number of properties that are likely to receive pressure below 1 bar (10 metres) with a flow of 9 litres per minute. This is the pressure most water companies aim for in order to maximise efficiency. In addition the Water Supply and Sewerage Services (Customer Service Standards) (Amendment) Regulations 1996 which are statutory, merely requires companies to maintain a minimum pressure of 0.7 bar (7 metres head) at the point of supply. ie the edge of the highway.

iv) Many kilometres of water mains, particularly in hilly areas will have pressures in them well in excess of 3.5 bar (35 metres) at all times now and in the future and will adequately supply many domestic sprinkler systems without further pumping.

v) However there are also many kilometres of mains which for most of the time have in excess of 3.5 bar pressure but for one or two hours each day at peak demand times the pressure will reduce to a lower amount, possibly less than 2 bar. Many of these and other mains will also have longer and even lower pressures in them during drought periods.

vi) In order to make the supply of water more efficient by reducing leakage and general consumption, pressure management is extensively applied across our distribution systems. Pressure in these mains is managed to generally between 15 and 25 metres head; which will require a pump to be fitted to most sprinkler systems in those areas. This has greatly contributed to Dwr Cymru Welsh Water (DCWW) reducing its leakage by 50% since 1995.

Pressure management will continue to spread over an increasing length of the mains, probably rendering them unsuitable for a sprinkler system without a pump.

Specification

The Dept CLG and the Fire Services are anxious to minimise installation costs to maximise the number of sprinkler system installations even though this may mean installing a system that will have inadequate pressure for small periods of time as described above. However BS 9251 expects a system to be designed that will operate properly at all times. There is concern in the Water Industry that even if the terms and conditions for the supply allowed for this downtime and the applicant accepted them, that the public and press would be very critical of any party involved with agreeing to such an installation if it resulted in subsequent loss of life.

In consequence of the above information on the pressure of mains water the following specification decisions need to be made by the Committee:-

Will systems be required to function properly 100% of the time with the current water main pressures (consideration needs to be given how householders will react to future reductions in pressure by the water supplier and the need for them to install at their own expense an expensive pump, switchgear and possibly a tank if the sprinkler system is to continue to function)  or

Will systems be required to function properly 100% of the time even if water main pressure reductions are carried out in the future or

Will systems be allowed that will not function properly, or at all, for small periods of time.

Pumps

To overcome deficiencies relating to pressure then it may be practical to fit a pump on the sprinkler supply pipe. If the rate of flow to the sprinklers would cause problems in the water main network, or the meter restricts the flow too much causing the pump to be starved of water, then storage will need to be considered. This can be filled slowly from the domestic supply pipe with water that has passed through the domestic meter. The storage needs to be adequate for 10 minutes operation for domestic sprinklers (ie 840 litres) and 30 minutes for residential sprinklers (ie 5040 litres [5.04 m3]). This arrangement will eliminate any problems with low water main pressures and metering. It will avoid the need to increase the connection and communication pipe sizes, the need for a branch pipe, a second meter, stop tap and chamber and a second supply pipe to the property. It has the disadvantage of the cost of storage, a pump and switchgear, the maintenance of the pump and the risk of interruption of the electricity supply to the pump caused by the fire.

Consideration might be given to the storage costs being shared with a rainwater harvesting system.

Future Maintenance

It is extremely important that any pump and the sprinkler system are regularly maintained if they are to work properly when needed and are kept completely isolated from the potable supply system. As water within the sprinkler plumbing may never be used it will become stagnant and deteriorate and could give rise to serious ill health if cross connected to the potable supply system or if the necessary backflow prevention devices malfunction. Serious consideration needs to be given how to ensure that this maintenance will be carried out regularly by householders who cannot afford or understand the importance of maintenance.

Keith Pratley

Water Regulations and Water Efficiency Manager

Dwr Cymru Welsh Water

25 April 2008