Solutions:

Air bubbles visible in strainer basket
Make sure pool water is at proper operating level (mid-skimmer).
Check to make sure skimmer weir(s) is/are not stuck.
Make sure pump strainer lid and gasket are sealed properly.
Clean all debris from strainer basket.

Low Flow
Check and clean skimmer baskets (poolside).
Check filter pressure - if 8 p.s.i. above normal - backwash filter.
Check pump strainer basket and clean as necessary.
Check pump impeller and remove any debris.
Re-prime pump - fill pump basket with water before re-starting.

No Suction For Vacuum
Make sure vacuum hose is primed (full of water).
Make sure filter is clean (backwash if necessary).
Make sure all baskets are clean.
Isolate vacuum line if necessary (close other appropriate suction line valves).

Heater Not Functioning
For millivolt heaters - make sure pilot is lit.
For electronic ignition heaters – make sure you have power.
Clean all baskets.
Check filter pressure. If filter is dirty (high filter pressure) backwash filter to increase flow.  The heater's pressure switch will not allow the heater to fire if it does not sense enough flow.  Backwashing the filter usually corrects this problem.

Water Balance
Keeping your water chemistry balanced is imperative to keeping a swimming pool clean, clear, and in good working order. The swimming pool's structure and filter system can be adversely affected if the water is not kept in balance. The following are the levels that we recommend for proper pool water balance:
 

Strong Odor/Eye Irritation: A common misconception among swimming pool owners and swimmers is that strong chlorine odor and eye irritation is due to high chlorine levels in the pool water. In actuality, the reverse is true. Strong chlorine odor and eye irritation are most commonly the result of a high level of combined chlorine present in the pool water. Combined chlorine is most commonly found in the form of chloramines (chlorine combined with ammonia from perspiration or other sources). This type of chlorine is not effective as a sanitizer and produces a strong chlorine odor, as well as irritating swimmer's eyes. Shocking the pool with a quick-release non-stabilized chlorine is recommended to eliminate chloramines. Thus; adding more Free Chlorine will solve the problem, not amplify it as is commonly misconstrued among pool users and owners.

Low pH Due To 3" Tablet Usage: If you use 3-inch stabilized tablets to chlorinate your pool, you should monitor your pH closely. 3-inch tablets have a pH of 2.4 and lower the pH of your pool water consistently over time. If ignored, the pH of your pool water can decrease drastically and lead to structural and equipment damage. We recommend testing your pH at least three times a week.