Before laying, you were supposed to add a 25mm layer of compost into the first 50mm of the soil. They will improve the soilâÂÂs nutrient and water-holding capacity. If the turf gets too spongy, set the mower on its slowest setting and cut the lawn right back. It is likely to look brown, but will grow back. Then keep moving at 20- 25mm, using a rotary or reel mower. Do not over water it.

Here is a link that might be useful: Maintenance

I don't think Ethan read your message before posting. Although you did apply compost, it was not required and certainly not required to incorporate it into the soil. Don't fret about that.

It would seem like you are watering far too long though. Was the sod rolled after laying it down? That might be one mistake. Rolling is needed to ensure the bottom of the sod meets the top of the underlying soil.

Do you know how much water your sprinkler puts out in an hour? All you need is enough to moisten the sod and the very top of the underlying soil. You might need that amount 3x per day for the first 2 weeks until the sod knits into the soil. Normally we talk about watering 5-15 minutes, 3x per day (breakfast, lunch, and dinner). Your soil should never be soggy while starting a new lawn. If yours has been then you might already have a fungal disease which is cutting off moisture to the grass plants.

Where do you live?
What kind of grass did you buy?