Asp.net async db connection not reusing connections - asp.net

Question

I have a .net mvc / sql server website for a high-traffic application. I'm using async database connections.
Prior to launch I ran a load test, and it blew up pretty quickly under load. The connection pool quickly ran out of connections.
Running sp_who at the database level shows a pile of connections sleeping awaiting command. If I switch to non-async, this does not happen.
So, it appears that new database calls are not using connections sitting in the connection pool, instead they are opening their own new connection. This quickly exhausts the connection pool limit, and begins timing out queries.
The following is the helper I'm using to execute an async datareader. Does anyone see any issue here?
private async Task<List<T>> ExecuteReaderAsync<T>(SqlCommand command, Func<SqlDataReader, T> rowConverter)
{
List<T> ret = new List<T>();
using (SqlConnection connection = new SqlConnection(this.ConnectionString))
{
command.Connection = connection;
await connection.OpenAsync();
using (SqlDataReader reader = await command.ExecuteReaderAsync())
{
while (await reader.ReadAsync())
{
ret.Add(rowConverter(reader));
}
reader.Close();
}
connection.Close();
}
return ret;
}
I'm calling the code like the datareader helper like the following:
public async Task<Content> FindContentAsync(int id)
{
Content content = null;
using (SqlCommand command = CreateProcedure("dbo.FindContent"))
{
AddParam(command, "Id", SqlDbType.Int, id);
List<Content> items = await ExecuteReaderAsync<Content>(command, x => BindContent(x));
if (items.Count > 0)
{
content = items[0];
}
}
return content;
}
And calling that from a helper:
public async Task<Content> FindAsync(int id)
{
var db = new DataAccess();
var content = await db.FindContentAsync(id);
return content;
}