Bulletin 27: Domestic Hot and Cold Water

Water pressure

As its name implies Ridge End sits on a ridge so that from time to time we have found that the pressure of the mains water supply to the property can be quite low. This is particularly so during hot spells in the summer when in the evenings it would seem that people come home from work and turn on their irrigation systems and take showers to freshen up after a hot sticky day. To ensure that the new house has a plentiful supply of water at an appropriate, constant pressure we have taken the decision to install a pair of water tanks in the basement plant-room that are filled from the incoming water main. From this local store booster pumps supply water all around the house at a good constant pressure.  Each tank has a foot print of roughly 1metre square and is 2metres high. Thus each tank has a capacity of 2 cubic metres so that they hold 2000 litres giving a total stored capacity of 4000 litres or 4 metric tonnes of water.

Water purity; avoiding legionella

One of the pitfalls of storing large volumes of water is that it must be kept sterile. To this end water from the tanks is constantly recirculated through an ultra violet steriliser. This works by passing the water from the tanks over an ultra violet (UV) lamp where the effect of its UV light is to kill any bacteria or algae that might form in the still water of the tanks. Once the water has passed through the UV lamp it is returned back to the tanks.

Cold water storage tanks. The cold water tanks are the tall rectangular structures to the left of the picture. The two cylindrical tanks to the right are the hot water heaters.

Cold water storage tanks. The cold water tanks are the tall rectangular structures to the left of the picture. The two cylindrical tanks to the right are the hot water heaters.

 

Dealing with “hard” water

 Another aspect of the mains water supply to Ridge End is that it contains calcium salts and so is quite “hard”. Hard water has the effect of furring up appliances such as washing machines, dishwashers, kettles etc with a hard lime-scale deposit. It also causes a nasty lime-scale deposit to build up on kitchen and bathroom sanitary ware. The way to avoid this is to use a water softener. Such a device is included in the Ridge End domestic water system design. This operates by transferring the calcium ions in the water for sodium ions through an ion exchange mechanism in a water softener. The resulting softened water containing sodium salts does not cause the furring associated with hard water since sodium salts are soluble. Unfortunately softened water is not good to drink as prolonged exposure to high levels of sodium in drinking water is liable to lead to human health problems such as high blood pressure. To get round this problem the ridge end water supply design supplies three types of water:

  • Boosted-pressure un-softened cold water to the two kitchen sinks and the boot room sink for drinking
  • Softened cold water to all sinks and bathrooms
  • Softened hot water to all sinks and bathrooms

Hot water supply

Hot water is supplied from a pair of water “calorifiers”.  A calorifier is an industry term for a storage vessel that has the capacity to generate heat within a mass of stored water. Essentially these are storage vessels that incorporate coiled pipes that sit in the body of stored water. By passing hot water from the house boilers through the pipe coils heat is transferred to the stored water to provide a supply of hot water to the house. These are shown in the photograph below.

The cold water storage tanks are shown on the left. The pumps that boost the cold water pressure to all parts of the house are shown in the middle of the picture. The two hot water calorifiers are the smaller, white vertical tanks to the right of the picture. The UV steriliser is the device mounted vertically on the wall.

The cold water storage tanks are shown on the left. The pumps that boost the cold water pressure to all parts of the house are shown in the middle of the picture. The two hot water calorifiers are the smaller, white vertical tanks to the right of the picture. The UV steriliser is the device mounted vertically on the wall.

Dual redundant resilience

It should be noted from the photograph above that all aspects are duplicated for redundancy. A single failure of any equipment will not deny hot or cold water from the house!  To this end the cold water storage tanks are duplicated and are filled from the incoming water main and connected to the system via independent connections. Similarly the hot water calorifiers are in a dual redundant, independent configuration.  The dual redundant pump configuration supplying the boosted pressure cold water operates with each pump on a weekly “duty cycle” so that the pump doing the work is changed over each week. The reason for this is to allow even wear on the pumps and to ensure that in the event that one of the pumps does fail and an automatic change-over is initiated the other pump is operational. If this weekly change over were not to be implemented it is likely that the standby pump would be dormant for a considerable time, perhaps years, before it was called to action. In this eventuality if it had never been actuated over such a prolonged time it is likely to be seized-up and so would fail also resulting in a catastrophic domestic water failure. Without this pumped water supply it will not even be possible to flush a lavatory or have any drinking water! This of course makes the house also vulnerable to an electrical power failure; but this will be dealt with in a subsequent blog bulletin.

Hot water supply

In a house of the size we are building here it would take a long time for the hot water to reach the bathroom taps or showers from the  hot water storage tanks/calorifiers in the basement. Furthermore it would be a waste of both water and energy. To overcome this problem the hot water is constantly circulated around the house via all the bathroom, kitchen and boot-room outlets in a “circulating hot-water main”. Accordingly it will only be necessary for the very short pipe from the main to the various faucets to be evacuated before hot water is delivered. The disadvantage of this of course is the complexity of having  “flow” and “return” pipework to and from the hot water tanks and the pumping mechanism to accomplish the hot water recirculation. This complication is more than adequately compensated for by the added convenience of fairly instant hot water and the reduced waste. The specification for the time delay to receive hot water at any of the hot-water taps is less than 5 seconds.

Domestic hot and cold water and central heating pipe runs passing from the main plant room along the ceiling of the games room in the basement.

Domestic hot and cold water and central heating pipe runs at the top left of the picture, passing from the main plant room along the ceiling of the games room in the basement.

Plumbing pipe runs in the ceiling void of the drawing room on the ground floor.

Plumbing pipe runs in the ceiling void of the drawing room on the ground floor. Note the hot and cold water tap-offs going through the concrete ceiling to one of the bathrooms above. The grey and white drainage pipe work taking foul water from the bathrooms above can also be seen.

 

All pipe-work is lagged. This picture show the same view as before with the pipe lagging installed.

All pipe-work is lagged. This picture show the same view as before with the pipe lagging installed.

More lagged pipe-work.

More lagged pipe-work.

The drawings that define the domestic hot and cold water supply are as follows and can be viewed by down loading them from the blog library:

Plumbing Schematic

Lower Ground Floor Domestic Water Services

Ground Floor Domestic Water Services

First Floor Domestic Water Services

Lower Ground Floor Drainage

Ground Floor Drainage

First Floor Drainage

 

 

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