how to delay using httpservice in angular6

Question

I want to use httpservice after a time delay. tried using

`import 'rxjs/add/operator/delay';`

however when I use delay in service;

this.httpService.put("http:addr?Id="+this.orgID, this.QRCodeImage).pipe(delay(3000)).subscribe(data => { console.log(data); });

'delay' is not getting recognized. however when I skip pipe and use delay, it gets recognized and throws error in console. How to delay sending an httpservice request.

Thanks :)