PROBLEM TO BE SOLVED: To obtain a water sealing tube with which reduction in heating installation costs and operation costs are conducted and in which lower limit temperature of crops is maintained in cold region and a region where solar radiation quantity is less, in shallow-layer heating system of a greenhouse for protected horticulture； and a method for using thereof.SOLUTION: A shallow-layer ground heating system comprises: a solar heat collection/accumulation bag body (1), which houses a heat collection/accumulation bag (3) high in solar light absorptivity in a transparent bag (2) high in transmittivity of solar light energy, and in which circulation piping (40) on going side and returning side is arranged, penetrating inside the heat collection/accumulation bag (3). The solar heat collection/accumulation bag body (1) is extendedly placed on a plowed soil layer (50) and communicates a heat source machine (45) with the circulation piping (40), wherein solar light energy is transmitted to a heat accumulation medium (W) inside the heat collection/accumulation bag (3) by warm water flowing the circulation piping (40), and the plowed soil layer (50) is heated and accumulates heat.【課題】 施設園芸ハウスの浅層加温システムにおいて、寒冷地や日射量が少ない地域で暖房設備費及び運転費の削減を実施し、作物の下限温度を維持する水封チューブ及び使用方法を得る。【解決手段】 太陽光エネルギーの透過率が高い透明バック（２）内に、太陽光の吸収率が高い集蓄熱バック（３）を収納し、集蓄熱バック（３）内を貫通して往き側及び還り側循環パイプ（４０）を配置する太陽集蓄熱バック体（１）を、作土層（５０）上に延伸載置し、熱源機（４５）と循環パイプ（４０）とを連通するものであり、太陽光エネルギーを集蓄熱バック（３）内の蓄熱媒体（Ｗ）に伝熱し、循環パイプ（４０）を流動する温水によって、蓄熱媒体（Ｗ）に伝熱して、作土層（５０）を加温蓄熱する浅層地中加温システム。【選択図】図１
