Hot water service is a plumbing system designed to provide an unlimited hot water supply for general household use.
It is usually regulated with a temperature-control valve, which can be adjusted to restrict flow. Most valves are designed so that the hot water becomes more relaxed as more cold-water mixes with it. These valves allow less than 1/4 of the cold feedwater to mix with the hot return before reaching the fixture furthest from the source. This design assures scalding safety since control ranges ensure only very cool water at distant outlets or shower mixing chambers.
How Does the System Work?
An alternative system allows the water heater to act as a boiler. Such methods include an unfiltered strainer or filter box connected between it and the hot water outlet; this allows debris to accumulate in the sieve instead of clogging valves downstream.
An indicator warns when the filter needs cleaning. The use of separate lines reduces noise that may occur with diluted cold-water feed into pressurized hot water lines, making these installations suitable for apartment buildings without disturbing tenants. Likewise, if someone flushes a toilet far away from the hot water distributing system, they can get scalded.
Water travels from the cold-water source, i.e., the municipal water primary, through 1/2″ copper tubing to an expansion tank located in the basement. The expansion tank allows for normal piping system movement due to temperature changes and other factors that cause systems to expand and contract. An air vent prevents pressure build-up in the piping system due to temperature changes or backflow caused by high wind or other causes. From here, 1/2″ copper tubing runs vertically up inside the center of 4″ metal pipes (risers) that connect each floor through their respective water shut valves. Each riser should have an accessible clean-out near its base, which aid in flushing the system. The hot water tank is located on each floor to provide immediate access to its respective floors’ cold and hot feeds.
On small systems (e.g., double story buildings), it may be more cost-effective to use 1″ piping or 3/4″ PEX tubing for both cold and hot feedwater instead of using two different sizes for both feeds. However, this does not allow for future expansion of the service if an additional floor is added later. It also precludes recycling of washing machine water back into the service (see below).
It is recommended that a 1″ copper pipe can be used as a submarine during installation to serve all taps from a single source. In this way, expanding services becomes easier in step with building additions without requiring additional piping runs to each outlet.
The hot water tank is usually an electric model, but gas-fired and even wood or pellet-fired models are sometimes used. All tanks either have a built-in anode rod (made of magnesium, aluminum, or zinc) or a separate magnesium anode bar soldered into each tank’s plumbing connections to corrode instead of the steel tank itself.
This keeps rust particles from microscopic crevices that would otherwise enlarge and perforate tank surfaces with time.
A sacrificial anode rod performs its corrosion duties for decades before needing replacement according to the manufacturer’s instructions; on occasion, these instructions are ignored by plumbers.
The tank is connected to the cold-water supply using a 1/2″ copper tube run up inside its riser tubes. A T&P relief valve is located at the top of the hot water tank, usually near the anode rod connection. This allows excess pressure to vent without breaking any of the plumbing connections to the tank itself. Hot water also flows through two 1/2″ copper lines out of each floor’s hot water riser and into a distribution manifold on the exterior side of the building’s foundation wall. From here, cold feedwater travels down 3/4″ CPVC tubing, which feeds all showerheads, tubs, lavatories, basins, etc.
Hence, after reading the above information, you might now be clear with the whole mechanism of the hot water service system.