Google tag assistant reports: “Same web property ID is tracked twice”

Question

I've added the following Google Tag and Google Analytics code in my website. When i checked with Google Tag Assistant (Chrome Addon), I can find a yellow indicator against Google Analytics Tag which says to optimize "Same web property ID is tracked twice." As well as i can see "2 Pageview Requests"

How could i resolve this? Is that because I've added both Google Tag Manager and Google Analytics? I need both Google Tag Manager and Google Analytics run together smoothly without these kind of issues.

Google Tag Manager and Google Analytics Script added below

<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-27898392-1"></script>
<script>    
    window.dataLayer = window.dataLayer || [];
    function gtag() { dataLayer.push(arguments); }
    gtag('js', new Date());
    gtag('config', 'UA-27898392-1');
</script> 

<!-- Google Analytics -->
<script>
    window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)};ga.l=+new Date;
    ga('create', 'UA-27898392-1', 'auto');
    ga('set', 'userId', '123456');
    //Custom-User-ID - index 1
    ga('set', 'dimension1', '123456');
    //Custom-User-Name - index 2
    ga('set', 'dimension2', 'jerome');
    //Custom-User-Email - index 3
    ga('set', 'dimension3', 'haijerome@gmail.com');
    //Custom-User-Customer-ID - index 4
    ga('set', 'dimension4', '123456');
    //Custom-User-Customer-Name - index 5
    ga('set', 'dimension5', 'Test');
    ga('send', 'pageview');
</script>
<script async src='https://www.google-analytics.com/analytics.js'></script>
<!-- End Google Analytics -->

Answer 1

Yes, just delete Google Analytics code from site, you should implement all tags you need through Google Tag Manager, That will solve your problem. Also i see you have Google Ads, if it is not, consider moving it to Google Tag Manager too, it will be easier for you to reconfigure it when ever you need it.

Answer 2

Google Tag Manager and Google Analytics Script added below

The script is not for Google Tag Manager..
You have the Global Site Tag gtag.js version and Universal Analytics version of GA tracking installed.
If you delete the following snippet:

<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-27898392-1"></script>
<script>    
    window.dataLayer = window.dataLayer || [];
    function gtag() { dataLayer.push(arguments); }
    gtag('js', new Date());
    gtag('config', 'UA-27898392-1');
</script>  

Then the yellow Same Web Property warning will go away and you will return to seeing only a single pageview being fired.

As per the 2nd tracking code snippet in your example (universal analytics with the custom dimensions)

<!-- Google Analytics -->
<script>
    window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)};ga.l=+new Date;
    ga('create', 'UA-27898392-1', 'auto');
    ga('set', 'userId', '123456');
    //Custom-User-ID - index 1
    ga('set', 'dimension1', '123456');
    //Custom-User-Name - index 2
    ga('set', 'dimension2', 'jerome');
    //Custom-User-Email - index 3
    ga('set', 'dimension3', 'haijerome@gmail.com');
    //Custom-User-Customer-ID - index 4
    ga('set', 'dimension4', '123456');
    //Custom-User-Customer-Name - index 5
    ga('set', 'dimension5', 'Test');
    ga('send', 'pageview');
</script>
<script async src='https://www.google-analytics.com/analytics.js'></script>
<!-- End Google Analytics -->

keep in mind it is against the GA TOS to use GA to track/store PII (Personally Identifiable Information) such as names, email addresses and so forth.

Having said all of that, i do agree that using Google Tag Manager would be the better way to go if trying to setup a variety conversion and site tracking.