Unit 205: Domestic hot water systems Sample question paper - Answers

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1 Unit 205: Domestic hot water systems Sample question paper - Answers Prepare Work Locations 1/ Which part of the Building Regulations lays down the requirements for the insulation of hot water pipework and cylinders in domestic properties? a) Part G b) Part H c) Part L1 d) Part P1 Part L1 - Conservation of fuel and power includes requirements for insulation of hot water pipework and storage cylinders. 2/ Which of the following documentation could be used on a new-build construction site to identify the required position of a hot water storage cylinder? a) Job specification b) Manufacturer instructions c) Block plan d) Building plans Building plans showing the details of the floor/component layout of a building will usually contain information such as the position of the hot water storage cylinder. 3/ Which of the following is the correct type of joint that can be used to make a connection between two sections of polybutylene hot water pipe? a) Push-fit fitting b) End feed capillary fitting c) Capillary solder ring fitting d) Fusion welded fitting Of the list, a proprietary push-fit fitting is the only type that would be used with a polybutylene (plastic) hot water pipe. Page 1 of 7

2 4/ The maximum recommended depth of notch in a first floor joist is a) 1/8 the joist depth b) 1/4 the joist depth c) 1/2 the joist depth d) 3/4 the joist depth The maximum recommended depth of notch in a first floor joist is 1/8 th the joist depth so if the joist depth is 200mm the maximum depth of notch is 200/8 = 25mm. Install Systems 5/ The following diagram shows an indirect hot water system, which section of pipe is missing from the diagram? a) Primary cold feed pipe b) Primary open vent pipe c) Secondary cold feed pipe d) Secondary open vent pipe The primary open vent pipe is missing from the drawing which should run from a tee at the highest point on the primary flow to the cylinder and terminate over the feed and expansion cistern. Page 2 of 7

3 6/ A single feed indirect cylinder works on the principle of a) Water compression b) Water siphonage c) Air entrapment d) Air expulsion A single feed indirect cylinder includes an air bubble to separate the primary and secondary waters from mixing, its working principle is therefore air entrapment. 7/ Which type of hot water storage cylinder is shown in the following diagram? a) Direct cylinder b) Combination unit c) Double feed indirect cylinder d) Single feed indirect cylinder The diagram shows a double feed indirect cylinder containing a coil through which the primary water circulates. The coil provides total separation of the primary and secondary waters and prevents them from mixing. 8/ The main reason why dead legs should be avoided in hot water systems pipework is in order to a) Prevent scalding b) Minimise corrosion c) Increase cylinder lifespan d) Prevent water wastage Long hot water dead legs to remote sanitary appliances result in a wastage of water and heat energy as excessive amounts of water may have to be drawn off before hot water reaches the tap. Page 3 of 7

4 9/ Which of the following can be used to overcome the problems associated with long dead legs in hot water systems pipework? a) Apply trace heating b) Apply localised cooling c) Fit a shock arrestor d) Fit a non-return valve Electric trace heating can be used with excessively long dead legs to heat the section of pipe, keeping the contents hot so that a limited amount of hot water is wasted when a tap is opened in the dead leg. 10/ Which of the following types of copper tube would normally be used to form the cold feed pipe to a hot water storage cylinder? a) R220 minibore coils b) R220 soft coils c) R250 half hard lengths d) R290 hard lengths R250 half hard lengths (old table X) would normally be used to form the cold feed pipe. 11/ Which type of servicing valve would normally be fitted to the cold feed pipe to a hot water storage cylinder? a) Screwdown stop valve b) Lever operated spherical plug valve c) Single check valve d) Fullway gate valve A fullway gate valve is normally fitted to the cold feed pipe as it is suited to low pressure applications. Page 4 of 7

5 12/ The minimum size of primary circulation pipework between a small solid fuel boiler serving a direct hot water cylinder only is a) 15mm b) 22mm c) 28mm d) 35mm The minimum pipe size for gravity primary circulators between a small solid fuel boiler and a direct cylinder is 22mm subject to sufficient circulating head and a minimum lengths of horizontal pipe run. 13/ The minimum recommended distance between the base of a cold-water storage cistern and the shower rose of a low-pressure shower is a) 250mm b) 600mm c) 900mm d) 1000mm Standard industry practice is to ensure a minimum head of 1m, however, manufacturer instructions must always be consulted to ensure that there is no variance from this standard industry guidance. 14/ What type of pump is shown in the following diagram? a) Single impellor booster pump b) Twin impellor booster pump c) Circulating pump d) Reciprocating pump The drawing shows a single impellor booster pump for boosting the supply pressure and flow rate to a shower. Page 5 of 7

6 Commission Systems 15/ The maximum working pressure of a copper hot water pipework system is 0.4 bar. What is the soundness test pressure to be applied to meet Water Regulation requirements? a) 0.2 bar b) 0.4 bar c) 0.6 bar d) 0.8 bar Water Regulations require that systems are tested to 1.5 times the maximum working pressure, so 0.4 bar x 1.5 = 0.6 bar pressure. 16/ What is the minimum gap required in a feed and expansion cistern between the finished (heated) water level and the invert level of the warning pipe? a) 10mm b) 25mm c) 50mm d) 100mm The minimum gap is 25mm, this measurement relates to the water level when the system is fully heated i.e. the cistern has received all the expanded water from the system. Decommission Systems 17/ When re-washering a hot bath tap the most efficient way of draining the hot supply to the tap is to isolate the a) Gate valve on the cylinder and drain through the cylinder drain valve b) Service valve on the storage cistern and drain through the hot bath tap c) Gate valve on the cylinder and drain through the hot bath tap d) Stop tap under the kitchen sink and drain through the hot bath tap Isolating the gate valve on the cylinder and opening the bath tap will only empty the contents of the pipe itself, the others will either drain the contents of the storage cistern or the cylinder. Page 6 of 7

7 18/ The safest method of ensuring that the hot water supply to open pipe ends is not re-activated while a plumber is away from site is to a) Leave a warning notice near the pipe ends b) Cap the pipe ends with stop ends c) Cap the pipe ends with timber plugs d) Nip the pipe ends closed Capping the open pipe ends with stop ends will ensure that if the water supply was to be turned on then no water could leak from the pipe ends, leakage and potential damage would occur with the other options. Maintain Systems 19/ What is the likely fault resulting from the method of cold feed pipe connection to the storage cistern as shown in the following diagram? Storage cistern a) No supply at the cold water taps b) No supply at the hot water taps c) Noise in the system d) Corrosion in the system Cold feed pipe to cylinder The cold feed pipe falling back to the cistern would suffer from an air lock which would either result in no flow, or a limited flow from the hot water taps. 20/ The appearance of water from beneath the hand wheel of a pillar tap, only when it is opened, can be remedied by a) Re-washering the tap b) Replacing the large fibre washer to the tap headgear c) Re-seating the tap with a tap re-seating tool d) Re-packing the gland The leakage from beneath the hand wheel only when the tap is opened signifies that the packing gland is leaking. Page 7 of 7