Water quality can have an impact on appliance longevity. Water
supplied to the Greentherm T9900 SE/i must be in accordance
with table 17 and fig. 26.
For water analysis data call your local water department, or if on
a well, have well water analyzed periodically. Heavy scale will
form if the combination of water total hardness and pH exceeds
the values specified in fig. 26 (grey area), Bosch recommends
consulting a local water treatment professional for water
TDS (total Dissolved Solids) mg/l or ppm 690
Table 17 Water quality
Water total hardness and pH values
6.5 - 8.5
mg/l or ppm 200
mg/l or ppm 2.0
mg/l or ppm 250
mg/l or ppm 1.0
mg/l or ppm 0.3
mg/l or ppm 0.05
mg/l or ppm 5.0
1. Total Harness and pH maximum values must be evaluated in
combination. Indicated maximum values will be reduced
according to fig. 26.
2. Combined values of total hardness and pH must be under
the indicated grey area. (e.g. the pair [180;8.3] [total
hardness; pH] is not acceptable).
Connecting the pressure relief valve (PRV)
A pressure relief valve is included in the box and must be
installed at the time of installation. No valve is to be placed
between the PRV and the heater. No reducing coupling or other
restriction may be installed in the discharge line. The discharge
line must be a minimum of 4" above a drain and installed such
that it allows complete drainage of both the PRV and the line.
The discharge line must be placed where it will not cause any
▶ Use the integrated port to install the PRV, see Fig. 27 .
▶ Tighten the PRV with the support of a wrench, see Fig. 27.
▶ Support all piping.
Plumbing Connections (with shutoff valves) and
Pressure Relief Valve
4.10 Water connections
Water connections are on top ONLY.
Bottom connections are drain/service ports with limited flow
Greentherm T9900 SE/i – 6 720 813 635 (2019/03)