Max Connection Pool capped at 100
In your connection string, specify max pool size=&lt;your desired max pool size&gt;.  So in other words, if you want to change max pool size to the value 500, your connection string could resemble this:

"data source=your_server; initial catalog=your_db; trusted_connection=true; max pool size=500"


Obviously I'm assuming so much with your other parameters, but this should give you a good idea how to proceed.  Connection pooling is client-side provider enforcement.  It's the client that will need to specify this max pool size setting, via the connection string.

Also, make sure you are closing or disposing of your connections properly, otherwise you will tie up connections.  Something like this (C#):

string connectionString = "data source=your_server; initial catalog=your_db; trusted_connection=true; max pool size=500";

using (SqlConnection dbConn = new SqlConnection(connectionString))
{
    using (SqlCommand sqlCmd = new SqlCommand())
    {
        sqlCmd.Connection = dbConn;
        sqlCmd.CommandText = "select 1;";

        // ... so on and so forth
    }
}


The using block (in C#) calls IDisposable.Dispose() upon completion.  You could also implement SqlConnection.Dispose() or SqlConnection.Close() in the finally block of a try/catch/finally block.

Reference:  MSDN Documentation on SqlConnection.ConnectionString property