Have not but it all comes down to expected performance and what you will want out of the unit.
Like any instantaneous heater like this, unless they are high powered (9-10Kw), the performance figures can be quite low at any reasonable flow rate, if you consider an average hand washing temp to be around 38 > 40DegC, until you get into summer and the CW temp rises but any other time of the year, performance can drop sharply.
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