One of the most popular science curriculums on the market, Apologia has colorful and bright pages that kids will love. The upper grades are written in an easy to understand style, which comes in handy when learning subjects such as Chemistry or Biology. Dr. Wile (the author), takes special care in writing the curriculum for homeschooling students.
1 Tap is used in the British Isles and most of the Commonwealth for any everyday type of valve, particularly the fittings that control water supply to bathtubs and sinks.
A check valve, clack valve, non-return valve or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. ball check valve in the open position to allow forward flow and closed position to block reverse flow. A ball check valve is a check valve in which the closing member, the movable part to block the flow, is a spherical ball. In some ball check valves, the ball is spring-loaded to help keep it shut.