Document where type converters aren' applied

docs/pages/docs/type_converters.md

@@ -177,3 +177,18 @@ your type converter.
 
 As an alternative to using JSON type converters, you can use a custom [`ValueSerializer`](https://drift.simonbinder.eu/api/drift/valueserializer-class)
 and pass it to the serialization methods.
+
+## Type converters and SQL
+
+In database rows, columns to which a type converter has been applied are storing the result of
+`toSql()`. Drift will apply the type converter automatically when reading or writing rows, but they
+are not applied automatically when creating your own [expressions]({{'Dart API/expressions.md' | pageUrl }}).
+For example, filtering for values with [`column.equals`](https://drift.simonbinder.eu/api/drift/expression/equals)
+will compare not apply  the type converter, you'd be comparing the underlying database values.
+
+On columns with type converters, [`equalsValue`](https://drift.simonbinder.eu/api/drift/generatedcolumnwithtypeconverter/equalsvalue)
+can be used instead - unlike `equals`, `equasValue` will apply the converter before emtting a comparison in SQL.
+If you need to apply the converter for other comparisons as well, you can do that manually with `column.converter.toSql`.
+
+For variables used in queries that are part of a [drift file]({{'SQL API/drift_files.md'| pageUrl}}), type converters will be
+applied by default if the `apply_converters_on_variables` [builder option]({{'Generation options/index.md'|pageUrl}}) is enabled (which it is by default).