1) Make sure you're not flooding the sod or seed. Twice a day might or might not be right (it's probably right for the seed, at about 10 minutes a shot, but may be saturating the sod too much if the soil underneath is already wet...or too little if you have a fast-draining soil).

1a) "This area is mostly clay." We usually skate over this comment because everybody says it and, 99% of the time, they are not correct. Clay soils are actually extremely rare. What most people have are poorly treated soils that are something else and, with the proper treatment, resource balancing, and care, will be nice soil. No soil drains at a rate such that dumping water on it will enable it to drain instantly, except for a highly-sandy mix, and you don't want one of those. My beautiful silt suffered severe runoff last night in a thunderstorm, resulting in zero erosion due to a thick turf and mulched gardens. Lecture ends. :-)

1b) " I haven't done any soil testing." To end up with a showcase lawn, this will be necessary. If you're looking for the average weedy, patchy lawn, you don't need to. For something in-between, get the test and work with the worst problem or two. I tend to recommend Logan Labs (currently open) and will happily give you a full read on that for free. Just get the basic $25 test, it's comprehensive, and will save you hundreds in guttershot treatments in the future.

2) Get that soil test. If it's really clay, you're going to need to work in tons (literally) of organic material over a period of years. But I doubt that. You can do an in-home jar test to see what you actually have, as well, at least at a first guess.

Water that seed twice a day, minimum (for April, that's fine). I assume they used a tri-mix, which includes bluegrass, so keep up the watering for 1 month (bluegrass takes forever and you want it because it self-repairs).

At that point, you can back off to once every other day watering unless the weather is extremely hot. Hold that for 2 weeks, then back off to every 3 days (or every 2 days). For two weeks.

You're going to need to hold every 3 days to every 4 days throughout the summer if it doesn't rain. Spring seedings are touchy and aren't going to forgive you for letting them go dry. Even so, expect losses if the weather gets scorching hot.

If so, plan to reseed a bit on August 15. Revert back to the twice-daily waterings on the newly-planted areas, probably on the sections that point into the Sun.

Your fall-seeded areas, having all fall and spring to adjust in, will tolerate next summer much better, but may still need a little coddling.

In-Home Jar Test

Take a nice tall-sided jar and fill it with soil about 8/10ths full. Add water and let it all soak.

Shake very well. You can lid this, but I recommend using aluminum foil.

Take a photo at 2 minutes and make sure to measure where the "settling" line is. That's sand.

Take a photo at 2 hours and make sure to measure where the "settling" line is. That's silt.

Take a photo at 2 days and make sure to measure where the "settling" line is. That's clay.

It's crude and awfully subtle sometimes, but it gives you an idea. So if you have 1 inch of sand, 2 inches of silt, and 1 inch of clay in the jar (preferably straight-sided as curved sides bollix the math), then 25% sand, 50% silt, and 25% clay. Or, a silty/medium loam.

In my case? Six grains of sand, 95% silt, and 5% clay. Welcome to eastern Pennsylvania! :-)

There can be issues in some soils, but your soil test will tell us that as well, and tell us that your jar test will need to be re-done with a solvent. You can, if you wish, simply use vinegar instead--it'll break up a calcium soil--but if you do, NEVER put a lid on the jar. Any calcium carbonate will react and out-gas and shatter the jar. Sometimes quite explosively. Hence the recommendation to always use aluminum foil to begin with; some water sources are slightly acidic.