cooled cold water coil 2 cold drainwater 8 causes chamber water to drop out of the chamber 5 cooling reservoir water 3 fig1 shows a dual cold water coil the inner being smaller copper and the outer being larger plastic also shown are added fins 5 d to drainpipe 4 level line 6 c indicates the level of chamber water 24 that is affected by change in drainpipe temperature the remaining reservoir water 3 is unaffected by cold drainwater 8 because chamber water 24 becomes heavier and stationary 0074 fig1 shows a perspective of drainwater heat exchanger 45 and how the components earlier described fit together fig1 and 14 show a model of the horizontal convection chamber 5 where it is installed at a slight angle common in plumbing drain systems here the water level 6 c in the chamber 5 has a maximum depth 5 m and so the chamber 5 must have high walls which therefore hold more water a more preferred arrangement to minimize water in chamber 5 is shown in fig1 where the chamber 5 is compartmentalized by dividers 30 c the water level 5 m is much lower and therefore the desired minimum volume in the chamber 5 is attained dividers 30 c also act as fins to enhance heat transfer many may be added to advantage 0075 fig1 is a perspective view of a vertical drainwater heat exchanger 50 showing the relationship to components already described 0076 fig1 shows how exchanger 50 can be added in series or.