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. duckbill valve is a check valve in which flow proceeds through a soft tube that protrudes into the downstream side. Back-pressure collapses this tube, cutting off flow. A pneumatic non-return valve. Multiple check valves can be connected in series.