Sink and Shower P-traps

I looked at a house "bathroom" for a friend today. He wanted an opinion and unfortunately, I didn't have one, so I'll ask youse.
There is a bathroom sink with its own P-trap under the sink. The sink's drain (ABS - in the basement below) runs into the drain (ABS) from the shower, also in the basement below. This drain has a P-trap for the shower and then the drain exits the basement.
Is it a problem having the drain for the sink have, essentially 2 P traps, its own and also the P-trap for the shower downstream?
Also, the vent stack (I forgot to get the size of this) for the sink is the same one for the shower and it's downstream of the shower's P-trap.
He says he hasn't had any problems with flow, though the shower and sink aren't used every day. All of the drain lines in the basement are 2" ABS
It's an older house and I assume the work was done by a previous homeowner.
Charles
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In typed:

I think that none of that would be a problem -- the 2 P traps, the on event, etc.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Monday, August 22, 2016 at 9:29:17 PM UTC-4, Charles Bishop wrote:

I guess it depends on your definition of "problem". Is it likely to cause some noticeable issue probably not, unless the line gets plugged and then the sink will cause backup in the shower. Is it to code, would it pass a plumbing inspection, probably not. Could it be flagged by a home inspector in the future, probably yes. When you see things like that you immediately start to wonder how it got that way and what else is screwy that could be worse.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.