https://www.google.com.au/#q=bond+angle+h2o

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109.5

If we do a similar arrangement of water, putting oxygen in the center, and using the two hydrogens and two lone pairs at the corners, we also come up with a tetrahedral arrangement. However, there is one important difference – the bond angles for water are not 109.5.

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For water, it’s the combination of tetrahedral bond angle coupled with repulsion between the electron pairs of oxygen that are not attached to hydrogen atoms. The tetrahedral angle is 109.5° but the repulsion reduces that to 104.5°.