Thanks! Yeah I feel like we haven't been there long enough to actually break something, haha! So I was wondering if it was maybe due to the way they ran the pipes.

Maybe, or perhaps the workers flushed something down the toilet that is now causing the slowdowns.

Should be under a warranty.

It could be a clogged or wrongly plumbed sewer vent. The vent pipes go up through the roof and will let air in and out as you are plunging, rather than the other toilet water gurgling like you describe.

Since the house is new call the GC... they can put a camera in there and sort it out easily enough

My first thought was improper venting. My second was workers dumped some trash down the toilet to "dispose" of it. Tell the contractor to fix it now and don't be satisfied until it flushes normally.

Old story only somewhat related.

My parents kitchen sink ( and things on that line) started having drain problems. Camera showed the drain line through the yard was ok (we had had root problems in the past). Turned out to be the vent line was stopped up from tree leaves, a large pin oak. Cleaned it out, then put a simple screen over the vent on the roof.

A rental we had had a similar problem. After we rooted the drain (nothing), we checked the vent. Found a magnet that a roofer had dropped down the vent pipe while picking up nails. It had been there quite a while.

This is a problem for the GC. They are going to find a clog / restriction in the system that has been there since construction and has just been getting worse.

So, if you are lucky it's just a rag or something that went down the drain during construction.

If you are not lucky, it's a defect in the drain plumbing.

They need to run the drain and then send a camera down to make sure there's no issue with the plumbing itself. The camera is a common tool now - but you want to be there, or have someone knowledgeable about plumbing there. to watch the monitor so that a defect doesn't get glossed over.