Can carbon monoxide contaminate water?
Contamination would occur if a sufficient quantity of carbon monoxide wouldn't just bubble through but 


would react with water to form an unhealthy product or 
is dissolved in water


Both isn't really true:


$\ce{CO}$ does not react under these conditions.
The solubility of $\ce{CO}$ in water at 20 °C is as low as $\mathrm{30\,mg\cdot L^{-1}}$ (GESTATIS database)