The roof inspection portion of the General Home Inspection will not be as comprehensive as an inspection performed by a qualified roofing contractor. Because of variations in installation requirements of the huge number of different roof-covering materials installed over the years, the General Home Inspection does not include confirmation of proper installation. Home Inspectors are trained to identify common deficiencies and to recognize conditions that require evaluation by a specialist. Inspection of the roof typically includes visual evaluation of the roof structure, roof-covering materials, flashing, and roof penetrations like chimneys, mounting hardware for roof-mounted equipment, attic ventilation devices, ducts for evaporative coolers, and combustion and plumbing vents. The roof inspection does not include leak-testing and will not certify or warranty the roof against future leakage. Other limitations may apply and will be included in the comments as necessary.

Flashing is a general term used to describe sheet metal fabricated into shapes and used to protect areas of the roof from moisture intrusion. Inspection typically includes inspection for condition and proper installation of flashing in the following locations: - roof penetrations such as vents, electrical masts, chimneys, mechanical equipment, patio cover attachment points, and around skylights; - junctions at which roofs meet walls; - roof edges; - areas at which roofs change slope; - areas at which roof-covering materials change; and - areas at which different roof planes meet (such as valleys).

Accurate inspection of the chimney flue lies beyond the scope of the General Home Inspection. Although the Inspector may make comments on the condition of the portion of the flue readily visible from the roof, a full, accurate evaluation of the flue condition would require the services of a specialist. Because the accumulation of flammable materials in the flue as a natural result of the wood-burning process is a potential fire hazard, the inspector recommends that before the expiration of your Inspection Objection Deadline you have the flue inspected by a specialist.

Inspection of heating systems is limited to basic evaluation based on visual examination and operation using normal controls. Report comments are limited to identification of common requirements and deficiencies. Observed indications that further evaluation is needed will result in referral to a qualified heating, ventilating, and air-conditioning (HVAC) contractor.

Inspection of heating systems typically includes:

- system operation: confirmation of adequate response to the thermostat;

- proper location;

- proper system configuration;

- component condition

- exterior cabinet condition;

- fuel supply configuration and condition;

- combustion exhaust venting;

- air distribution components;

- proper condensation discharge; and

- temperature/pressure relief valve and discharge pipe: presence, condition, and configuration.

A representative sample of the visible heating distribution components (duct work) were inspected. Full inspection of all  duct work is not possible in areas/rooms where there are finished walls, ceilings and floors. Video inspection of duct work is not part of a general home inspection and should be completed if desired by a qualified HVAC contractor who provides such inspections.

Inspection of the plumbing system typically includes visual examination of:

- water supply pipes;

- drain, waste and vent (DWV) system;

- water heater (type, condition and operation);

- sewage disposal system (designation as public or private);

- gas system; and

- sump pump (confirmation of installation/operation).

I recommend flushing & servicing your water heater tank annually for optimal performance. Water temperature should be set to at least 120 degrees F to kill microbes and no higher than 130 degrees F to prevent scalding. 

Here is a nice maintenance guide from Lowe's to help. 

This water heater was gas-fired. Gas water heaters heat water using a gas burner located in a chamber beneath the water tank. The gas control mechanism contains safety features designed to prevent gas from leaking into the living space if the burner should fail for some reason.  Gas-fired water heaters must be properly installed so that the gas fuel is safely delivered to the water heater and so that the water heater safely exhausts the products of combustion to the home exterior. Gas-fired water heaters can be expected to last the length of the stated warranty and after its expiration may fail at any time.

This was an electric water heater. This type of water heater uses electric elements to heat water in the tank. These elements can often be replaced when they burn out. With heaters having two heating elements, the lower element usually burns out first. Heating elements should be replaced only by qualified plumbing contractors or HVAC technicians.

Hot water for the home was supplied by an electric tankless water heater. Tankless water heaters do not store water in a tank like conventional water heaters. When a hot water fixture is opened in the home, water flows into the water heater where it is heated by gas burners before flowing to the open hot water fixture. Tankless water heaters save energy by avoiding the stand-by losses associated with conventional water heaters which must constantly maintain water in a tank at a minimum temperature. Due to calcium build-up on components, tankless water heaters typically require service annually. Failure to service the water heater in a timely manner typically results in a reduced hot water flow rate. The Inspector recommends inspection by a qualified contractor.