Chapter 81: The supply of water

Chapter 81: The supply of water

¶81.1 There were understandable concerns that there might have been a failure on the part of the utility company to make as much water available as possible on 14 June 2017 for firefighting purposes or a failure by the LFB to make the most effective use of the water that was available. We therefore considered it appropriate to investigate the supply and use of water in order to find out whether there had been any shortcomings and, if so, how they might be avoided in the future.

Regulatory requirements

¶81.2 Fire and rescue authorities have a statutory duty to take all reasonable measures for securing that an adequate supply of water will be available for the authority's use in the event of fire.^16531653 Section 38 of the Fire and Rescue Services Act 2004. If a fire and rescue authority asks for a greater supply and pressure of water than a water company would otherwise provide, the water company must take all necessary steps to comply and may shut off the water in any area to do so.^16541654 Section 40 of the Fire and Rescue Services Act 2004.

¶81.3 Due to the vast volume of water available in the Barrow Hill and Willesden reservoirs and accessible through the Thames Water Ring Main, there was more than enough water available to meet the demand for firefighting at Grenfell Tower.^16551655 Stoianov, Water Expert Report {ISTRP00000008/229} paragraphs 3-5.

¶81.4 The minimum water pressure in the network at the location of the hydrants used by the LFB was about 25 metres (2.5 bar),^16561656 Stoianov, Water Expert Report {ISTRP00000008/237}. which exceeded both the minimum regulatory pressure of 7 metres (0.7 bar)^16571657 Regulation 17G(1) of the Water Supply and Sewerage Services (Customer Service Standards) Regulations 2008. and the 15 metres (1.5 bar) recommended by Ofwat.^16581658 Stoianov, Water Expert Report {ISTRP00000005/48} paragraph 2; Stoianov, Water Expert Report {ISTRP00000008/234-5} paragraph 29. There is no minimum pressure requirement applicable to the provision of water for firefighting.

Water companies and the water distribution system

¶81.5 The water used for firefighting at Grenfell Tower was drawn from the general water distribution system, a complex network of pipes and valves used to transport water from storage (such as reservoirs and water towers) to customers and hydrants. The function of the water distribution network is to deliver an appropriate quantity and quality of water at a suitable pressure with minimal leakage, which it achieves using the force of gravity and the use of pumps.^16591659 Stoianov, Water Expert Report {ISTRP00000003/5}.

¶81.6 Thames Water Utilities Limited (Thames Water) is the company which supplies water to London, including the Barrow Hill Zone in which Grenfell Tower is located. The Barrow Hill Zone is supplied by water from the Barrow Hill and Willesden reservoirs and has access to additional capacity provided by the Thames Water Ring Main.^16601660 Stoianov, Water Expert Report {ISTRP00000008/229}.

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¶81.7 When fire and rescue authorities require water for firefighting, they connect fire hoses to hydrants to deliver water to pump appliances, which in turn pump it through hoses to firefighting equipment.^16611661 Stoianov {Day288/12:4-12}; Stoianov, Water Expert Report {ISTRP00000003/8-9}.

¶81.8 The three most important factors affecting the supply of water from a distribution network to firefighting equipment are:^16621662 Stoianov, Water Expert Report {ISTRP00000003/17-18}. a. The quantity of water available, that is, the volume of water in the distribution network

that can be made available through hydrants, which determines the time for which water can be provided to appliances.

¶b. The rate at which water can be extracted from fire hydrants for delivery to pump appliances. The flow rate describes the volume of water passing through a pipe or hose in a given time.^16631663 Stoianov, Water Expert Report {ISTRP00000003/20}. The flow rate provided by any particular hydrant is dependent on many factors, including the water pressure in the pipe supplying it, the hydrant's flow coefficient (a measure of the flow rate the hydrant can provide given the pressure of water it receives),^16641664 Stoianov {Day288/19:3-9}. and the energy losses between the hydrant and the pump appliance (such as those caused by gravity or by kinks in the hose).

¶c. The flow rate and water pressure at the discharge point of the firefighting equipment itself. There is a maximum flow rate and pressure at which any piece of equipment can safely be operated that are determined by the manufacturer.^16651665 Stoianov, Water Expert Report {ISTRP00000006/3}; Stoianov {Day288/23:17}-{Day288/24:18}. Supplying water to equipment at less than its maximum rated flow rate or pressure reduces the size of the water jet produced. The flow rate and pressure of water at the firefighting equipment depends on the flow rate and pressure of water pumped out of the pump appliance and on the extent of energy losses between the appliance and the firefighting equipment.

The use of water at Grenfell Tower

¶81.9 At the Grenfell Tower fire the LFB used fire hoses to draw water from the four hydrants shown in Figure 81.1 below: H1, a fire hydrant located to the south-east of the tower under Grenfell Walk,^16661666 Stoianov, Water Expert Report {ISTRP00000008/76}. H3, a fire hydrant located at the intersection of Grenfell Road and Bomore Road,^16671667 Stoianov, Water Expert Report {ISTRP00000008/78}. H8, a fire hydrant located on Bramley Road^16681668 Stoianov, Water Expert Report {ISTRP00000008/86}. and H5, a wash-out hydrant located next to the Kensington Leisure Centre, which was wrongly labelled as a fire hydrant. (Wash-out hydrants are used by water companies for operational and maintenance purposes to flush out sediment and stagnant water, generally at significantly lower flow rates than fire hydrants. They are not designed to supply water for firefighting.)^16691669 Stoianov, Water Expert Report {ISTRP00000008/79}.

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¶Figure 81.1: The four hydrants, highlighted in yellow, used to supply water at Grenfell Tower on 14 June 2017.

¶81.10 On 14 June 2017, between the first deployment of water at 01.15 and about 13.00,^16701670 Stoianov, Water Expert Report {ISTRP00000006/8}. the LFB projected water on to the external face of the tower using aerial appliances, ground monitors and handheld branches.

¶81.11 Aerial appliances are fire engines with extendable ladders or cages from which water can be directed onto buildings.^16711671 Stoianov {Day288/30:16-19}. Three aerial appliances were deployed at Grenfell Tower: turntable ladder A213 TL (from 01.47 to 02.05),^16721672 Stoianov, Water Expert Report {ISTRP00000006/7} 'Jet B'. aerial ladder platform A245 (for less than a minute at 02.13, from 03.28 to 06.47 and from 07.14 to 09.45)^16731673 Stoianov, Water Expert Report {ISTRP00000006/7} 'Jet D'. and Surrey Fire and Rescue Service's aerial ladder platform S13A1 (from 10.47 onwards).^16741674 Stoianov, Water Expert Report {ISTRP00000006/7} 'Jet E'.

¶81.12 Ground monitors are water nozzles which sit in a frame, enabling them to be placed on the ground and aimed in a particular direction without needing to be held by firefighters.^16751675 Stoianov {Day288/31:3-10}. Two ground monitors were used, albeit intermittently, at Grenfell Tower. One was sited on Grenfell Walk to the south-east of the tower (from 02.41 to 11.30)^16761676 Stoianov, Water Expert Report {ISTRP00000006/7} 'Jet C'. and another on the terrace of the Kensington Aldridge Academy to the north-west of the tower (from 02.43 to 10.52).^16771677 Stoianov, Water Expert Report {ISTRP00000006/8}; {ISTRP00000006/26} 'Jet H'.

¶81.13 Branches are nozzles attached to fire hoses held by firefighters.^16781678 Stoianov {Day288/28:14-16}. Many handheld branches, including the first jet projected towards the window of Flat 16 from 01.15, were used at different times to project water onto the tower.^16791679 Stoianov, Water Expert Report {ISTRP00000006/7-8} 'Jet A', 'Jet H', 'Jet I', 'Jet J'. Many were also used to extinguish burning debris on the ground surrounding the building.^16801680 Stoianov, Water Expert Report {ISTRP00000006/7-8}; {ISTRP00000006/25-26} Jet F', 'Jet G', 'Jet I', 'Jet J'.

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¶81.14 Water for firefighting inside the tower was supplied through the building's dry rising main from 01.06,^16811681 Stoianov, Water Expert Report {ISTRP00000006/18}. and through an additional improvised fire hose into the south-west corner of the building from about 03.30.^16821682 Stoianov, Water Expert Report {ISTRP00000006/8} 'Supply K'.

¶81.15 None of the aerial appliances or ground monitors deployed at the incident was supplied at its maximum capacity due to restricted flow rates at the hydrants.^16831683 Stoianov, Water Expert Report {ISTRP00000006/236} paragraph 2. That had three consequences. a. First, it limited the vertical reach of the water jets directed onto the exterior of the

building.^16841684 Stoianov, Water Expert Report {ISTRP00000006/236} paragraph 2. Appliance A213 produced a jet with a maximum vertical reach of 50–52 metres (floors 18–19).^16851685 Stoianov, Water Expert Report {ISTRP00000006/20} lines 31-32. Appliance A245 reached a maximum height of approximately 35 metres (floor 13).^16861686 Stoianov, Water Expert Report {ISTRP00000006/24} lines 8-9. Appliance S13A1 reached a maximum height of approximately 47 metres (floor 17).^16871687 Stoianov, Water Expert Report {ISTRP00000006/174} lines 26-28. If supplied at their maximum rated flow and pressure, each of them was capable of projecting a water jet reaching the full height of the tower (approximately 65 metres).^16881688 Stoianov, Water Expert Report {ISTRP00000006/238} paragraph 3; Stoianov {Day288/42:12}-{Day288/43:23}.

¶b. Secondly, the rate at which water was supplied to the pump appliances did not always match that at which it was being pumped out to firefighting equipment, which in turn resulted in periodic interruptions in the use of some equipment.^16891689 Stoianov {Day288/62:1}-{Day288/63:3}. c. Thirdly, some firefighting equipment could not be used as intended.

¶81.16 In the light of the report produced for the Inquiry by Dr Stoianov, the LFB carried out a series of tests to determine the maximum height of the jet that could be practically achieved by aerial appliances and ground monitors of the kind used at Grenfell Tower.^16901690 {LFB00123672}, 'Flow tests conducted on aerial appliance types used at Grenfell Tower fire'. The maximum heights achieved during the tests were (with one exception) higher than those achieved on 14 June 2017, but not high enough to reach the top of the tower.^16911691 {LFB00123672/16}, 'Conclusions'' {ISTRP00000006/236-238}. In his supplementary report^16921692 Stoianov, Water Expert Supplemental Report {ISTRPS00000001/21-28}. and oral evidence to the Inquiry,^16931693 Stoianov {Day288/53:4}-{Day288/56:20}. Dr Stoianov made strong, and in our view, persuasive, criticisms of the testing method used by the LFB, most significantly, that it had failed to supply the appliances with water at their maximum rated flow rates or pressures. For that reason, he did not accept its conclusion that the aerial appliances were unable to project a water jet to a height of 65 metres.

¶81.17 Although Dr Stoianov's calculations provide some helpful indication of the maximum height that aerial appliances could reach in optimal conditions, he rightly accepted that there were matters beyond his knowledge and expertise that could limit the height to which a water jet could be projected in practice. They included weather conditions,^16941694 Stoianov {Day288/57:7-19}. the performance of pump appliances^16951695 Stoianov {Day288/58:8}-{Day288/59:4}. and, most significantly, operational factors affecting the use, siting or angle of the jet.^16961696 Stoianov {Day288/59:6-14}. Examples include obstructions impeding the siting of appliances, including burning debris falling from a building,^16971697 Stoianov {Day288/59:6-14}. and a possible reduction in the firefighting effectiveness of a jet when operated at the limit of its vertical reach.^16981698 Stoianov {Day288/59:15-25}.

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¶81.18 For these reasons, we cannot safely make any finding about the height to which aerial appliances might have been able to project water on 14 June 2017 if they had been supplied at their maximum rated flow and pressure. However, we have no hesitation in accepting Dr Stoianov's opinion that the height of the jets produced by the aerial appliances at Grenfell Tower was limited by the low flow rates at which water was supplied to the pump appliances.

¶81.19 An example of periodic interruptions in the use of equipment caused by low flow rates can be seen in the operation of appliance A213 from 01.47 to 02.05. The tank of the pump appliance supplying it repeatedly became empty after less than a minute, requiring A213's water jet to be interrupted for about 20 seconds to allow the tank to refill before it could be started again. Firefighter Raymond Keane improvised a partial solution by turning down the settings of the pump supplying A213, resulting in a continuous, but less powerful, jet.^16991699 Stoianov, Water Expert Report {ISTRP00000006/20} lines 20-28. Similarly, the initial operation of appliance A245 at 02.13 lasted for only 47 seconds until the tank of the pump supplying it became empty.^17001700 Stoianov, Water Expert Report {ISTRP00000006/23} lines 17-24. The same problem affected the ground monitor on Grenfell Walk and aerial ladder platform S13A1, resulting in repeated stoppages throughout their operation.^17011701 Stoianov, Water Expert Report {ISTRP00000006/22} lines 24-29; {ISTRP00000006/24} line 30 -{ISTRP00000006/25} line 2.

¶81.20 Aerial ladder platform A245 was one piece of equipment that could not be deployed as originally intended. Following its redeployment at 03.28, the flow rate delivered to A245 was too low to enable its monitor to be used effectively. Firefighters therefore improvised by strapping a smaller 22 mm high-pressure hose to the cage of A245 to produce a jet which could reach the tower,^17021702 Stoianov, Water Expert Report {ISTRP00000006/23} lines 25-30. the equivalent of pinching the opening of a garden hose to produce a longer but narrower stream of water.^17031703 Stoianov {Day288/64:22}-{Day288/65:7}. Similarly, the flow rate delivered to S13A1 was insufficient to make use of its built-in monitor without interruption and firefighters tried using a smaller diameter hose to produce a jet that could reach the tower. However, that was unsuccessful and they reverted to using the monitor of S13A1 for 20 seconds and then waiting about a minute for the tank of the pump supplying it to refill.^17041704 Stoianov, Water Expert Report {ISTRP00000006/24-25}.

¶81.21 One significant factor contributing to the low flow rates delivered at the outlets was a loss of pressure in the hoses between the hydrants and the pump appliances.^17051705 Stoianov, Water Expert Report {ISTRP00000006/238} paragraph 6; Stoianov {Day288/91:14-19}. Some pressure loss is unavoidable, but on the night of the fire this was exacerbated by the long distance from the hydrants to the tower (about 95 metres and 125 metres for hydrants H3 and H8 respectively). Those losses were partially redressed by using pumps in relays (i.e. two pump appliances deployed in series) for hydrant H8 and, from about 06.00 onwards, for hydrant H3.^17061706 Stoianov, Water Expert Report {ISTRP00000006/11}lines 32-37; {ISTRP00000006/239} paragraph d. The main cause of the problem, however, was the low flow rates delivered by the hydrants themselves,^17071707 Stoianov {Day288/91:14-19}. which were caused principally by the following three factors:^17081708 Stoianov, Water Expert Report {ISTRP00000006/238} paragraph 6; Stoianov {Day288/91:7-11}.

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¶a. the low flow coefficients of the fire hydrants; b. the use in one case of a wash-out hydrant instead of a fire hydrant; and

¶c. the continued use of pressure reduction mechanisms in the water distribution network and a lack of efficient co-ordination between the LFB and Thames Water.

¶81.22 Water companies have a statutory duty to keep all fire hydrants attached to their pipes in good working order and to replace any hydrant when necessary.^17091709 Section 57 of the Water Industry Act 1991. British Standard 750:2012^17101710 "Specification for underground fire hydrants and surface box frames and covers". (BS 750) states that fire hydrants should have a flow coefficient of not less than 92.^17111711 {BSI00001767/13} paragraph 10.2. BS 750 does not state whether that relates to a simple hydrant tested under factory conditions or to a hydrant installed in the pipework necessary to connect it to the water network. The distinction is relevant because the flow coefficient of a hydrant installed in a pipework system will necessarily be lower than (or, at best, equal to) that of a simple hydrant due to pressure losses introduced by the connecting pipework.^17121712 Stoianov {Day288/69:20-24}.

¶81.23 Paragraph 10.2 of BS 750 requires the flow coefficient of a fire hydrant to be specified in the manufacturer's literature. If the flow coefficient of a hydrant installed in a pipework system may be affected by pressure losses introduced by the particular characteristics of the connecting pipework, as Dr Stoianov told us was the case, its performance in service will, or may, depend to some extent on the system into which it has been incorporated, which is inherently variable and not something of which the manufacturer could be aware. We therefore think that the requirement in BS 750 must be understood as relating to the hydrant tested under factory conditions. However, it would avoid confusion if the British Standards Institution were to make the position clear.

¶81.24 Testing carried out by Dr Stoianov showed that the flow coefficients of the fire hydrants used at Grenfell Tower ranged between 31 and 74.^17131713 Stoianov, Water Expert Report {ISTRP00000008/100}; Dr Stoianov also tested three other hydrants in the vicinity of Grenfell Tower. All three had similar flow coefficients of between 32 and 58. As the hydrants were installed in the network, he was unable to test their factory standard flow coefficients. We have not had access to the manufacturers' literature relating to those hydrants and do not know whether their flow coefficients under factory conditions were 92, as required to conform to BS 750. However, Dr Stoianov told us that he would expect the installation of hydrants to be carried out in such a way as to maximise their flow coefficients and that he would have expected the flow coefficients of the hydrants used at the Grenfell Tower fire to be higher.^17141714 Stoianov {Day288/77:9}-{Day288/78:5}. If that had been the case, they would have provided greater flow rates to firefighting appliances and equipment.

¶81.25 Hydrant H5, which was used to supply aerial appliances A245 and S13A1, is not a fire hydrant but a wash-out hydrant, which is not designed to supply water for firefighting. It had a flow coefficient of 31, lower than the flow coefficients of the other three hydrants used at the Grenfell Tower fire, which ranged between 50 and 74.^17151715 Stoianov, Water Expert Report {ISTRP00000008/100}. Hydrant H5 had been wrongly labelled as a fire hydrant. The labelling of the hydrant was the responsibility of Thames Water.^17161716 Section 42 of the Fire and Rescue Services Act 2004.

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¶81.26 On 14 June 2017, neither the LFB nor Thames Water realised that H5 was a wash-out hydrant, although its status was indicated on Thames Water's Geographical Information System,^17171717 Stoianov, Water Expert Report {ISTRP00000009/21} paragraph 2. to which its technicians and the staff of its Network Management Centre referred during the incident.^17181718 See {THA00000036}. Having been mislabelled as a fire hydrant, there was no practical way for firefighters to tell that H5 was in fact a wash-out hydrant.^17191719 Stoianov {Day288/85:8}-{Day288/86:13}.

¶81.27 In his evidence to the Inquiry, Dr Stoianov said that he had notified Thames Water of the mislabelling of H5 while undertaking hydraulic testing in 2018.^17201720 Stoianov {Day288/87:16-21}. At some point between September 2018 and July 2019, Thames Water then replaced the metal frame of the wash‑out chamber and the metal lid of H5 with a correctly labelled "W" plate.^17211721 Stoianov, Water Expert Report {ISTRP00000008/79} lines 24-26; {ISTRP00000008/81} figure 6-37.

Thames Water's interventions in the network

¶81.28 The LFB contacted Thames Water's Network Management Centre by telephone at 01.28 on 14 June 2022 to ask for the attendance of a water technician and an increase in the water pressure.^17221722 {THA00000012/2}. Two water technicians attended the incident at 02.15 and two more at 04.15, followed by two more at approximately 07.30. After the initial call and subsequent confirmation from Thames Water that technicians were on their way, there was no further direct contact between the LFB's control room and Thames Water. Communications between the LFB and Thames Water took place between firefighters and water technicians at the incident ground. They included two requests from the LFB to increase the supply of water, one from WM Beale at about 02.30 and one from SM Payton at about 10.05.^17231723 Stoianov, Water Expert Report {ISTRP00000009/91-92}.

¶81.29 Thames Water made two changes to the water distribution network in an attempt to increase the amount of water available for firefighting. Technicians opened two boundary valves, at 03.09^17241724 Stoianov, Water Expert Report {ISTRP00000009/85} paragraph 1(a). and 11.05^17251725 Stoianov, Water Expert Report {ISTRP00000009/85} paragraph 1(b). respectively, with the aim of increasing the water pressure in the area around Grenfell Tower by connecting it to different parts of the water network and so spreading any pressure losses across a larger area.^17261726 Stoianov, Water Expert Report {ISTRP00000009/26} lines 12-17; Stoianov {Day288/94:16}-{Day 288/95:1}. However, that did not significantly increase the pressure at the hydrants being used by the LFB. It therefore had no significant effect on the flow rate at those hydrants^17271727 Stoianov, Water Expert Report {ISTRP00000009/85} paragraph 2; Stoianov, Water Expert Report {ISTRP00000008/213-214}. and caused no material improvement in the supply of water to the firefighting equipment.^17281728 Stoianov {Day288/95:24}-{Day288/96:8}.

¶81.30 Technicians from Thames Water also provided assistance at the incident ground. Between 06.00 and 06.30 they helped to clear blocked drains that were causing flooding around the tower and hindering firefighters' access to the building. At approximately 06.30, a technician opened fully the valve on a hydrant which had previously been only partially opened, resulting in an increased flow.^17291729 Stoianov, Water Expert Report {ISTRP00000009/86} paragraph 4.

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¶81.31 Water companies commonly use pressure reduction valves at certain points in the network to minimise water leaks and burst pipes, which are more likely to occur at higher pressures.^17301730 Stoianov, Water Expert Report {ISTRP00000005/8} section 4.1.2.1. During normal operations in June 2017, Thames Water operated a pressure reduction scheme in the Grenfell Tower area, which was implemented by the use of pressure reduction valves which it could operate remotely.^17311731 Stoianov, Water Expert Report {ISTRP00000008/47-48}; {ISTRP00000008/224} lines 9-13. On 14 June 2017, the pressure reduction valves remained open throughout the incident, which Dr Stoianov estimated resulted in a reduction in water pressure of between 0.7 and 1.3 bar.^17321732 Stoianov, Water Expert Report {ISTRP00000008/231} paragraph 13. At 03.55, the Thames Water's Network Management Centre told the technicians at the incident how to switch off the pressure reduction valves, but the technicians decided against doing so because they were concerned that if the pressure became too high it might burst the pipes, a decision with which the Network Management Centre appears to have agreed.^17331733 Stoianov, Water Expert Report {ISTRP00000009/103-104} paragraph 52. If a pipe had broken, it could have led to the loss of a substantial amount of water and a widespread loss of pressure, putting the entire water supply to Grenfell Tower at risk.^17341734 Stoianov {Day288/111:12-20}.

¶81.32 We think it likely in the light of Dr Stoianov's evidence that the pressure reduction system could have been switched off to produce an increase in water pressure of 0.7 to 1.3 bar, with only a minimal risk of a broken pipe,^17351735 Stoianov, Water Expert Report {ISTRP00000009/106} section 7.8.7. although that would have provided only a modest increase in the flow rate from the hydrants of between about 180 and 420 l/ min.^17361736 Stoianov, Water Expert Report {ISTRP00000008/236} paragraph (iii); Stoianov {Day288/107:6-21}. A single handheld firefighting branch requires a flow rate of 400 l/min.

¶81.33 Another feature of the day-to-day operation of the water distribution system at Grenfell Tower was the automatic cycle of the Hammersmith pumping station. The Hammersmith pumps operated to increase water pressure in the area during the day, when demand from customers was higher, and were automatically switched off between 00.30 and 05.30, when demand was lower. On 14 June 2017, the pumps operated as normal.^17371737 Stoianov, Water Expert Report {ISTRP00000008/11} paragraph 1. At 02.59, Thames Water appears to have decided against switching on the pumping station, again due to the risk of bursting a pipe.^17381738 Stoianov, Water Expert Report {ISTRP00000009/30}. In the light of Dr Stoianov's evidence we think that the Hammersmith pumps could have been switched on before 05.30 to increase the pressure available in the network with a minimal risk of breaking a pipe,^17391739 Stoianov, Water Expert Report {ISTRP00000009/102-103}; {ISTRP00000009/106} paragraph 59. but again, that would have provided an increase in the flow rate at the hydrants of only about two to three litres per minute.^17401740 Stoianov {Day288/104:12}-{Day288/105:14}. Given the scale and intensity of the fire, it is difficult to see that that would have made any significant difference to the LFB's firefighting efforts.

¶81.34 We should note that Dr Stoianov was critical of the level of technical and engineering support provided by the Thames Water's Network Management Centre during the incident. In particular, he thought that better use of available data, modelling and information about the network might have allowed it to recommend more efficient arrangements for the supply of water.^17411741 Stoianov, Water Expert Report {ISTRP00000009/99-102}. However, it seems unlikely that they would have secured a significantly greater supply.

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Misunderstandings about the water network

¶81.35 Dr Stoianov drew our attention to several misunderstandings and incorrect assumptions made by firefighters and Thames Water personnel on 14 June 2017 about the water network. Most notably, they included: a. confusing flow rate, pressure and volume;^17421742 Stoianov, Water Expert Report {ISTRP00000009/97} paragraph b; Stoianov, {ISTRP00000009/91} paragraph 19(a). b. an incorrect assumption that the water supply from a hydrant was reduced because water was being drawn from other hydrants, or as a result of "overuse";^17431743 Stoianov, Water Expert Report {ISTRP00000006/239-240} paragraph 8(a); Stoianov, Water Expert Report {ISTRP00000009/89} paragraph (b). and

¶c. a misunderstanding by technicians that it was possible by opening the boundary valve to give firefighters more flow to work with without increasing the water pressure, whereas increasing the pressure in the network was the only way to increase the flow rate from the hydrants.^17441744 Stoianov, Water Expert Report {ISTRP00000009/98} paragraph (e); see also {ISTRP00000009/101} paragraph (c).

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