What are you trying to water?
If you take a soaker hose an put it on top of an empty bucket you'll see how much water comes out over the course of an hour. You may be surprised. And slow soaking is a good way to water clay soil.

Thanks Quirky, I'll try the bucket thing. I am trying to water everything - vegetable garden (great amended soil), roses (somewhat amended soil), annuals and perennials in beds, shrubs planted within the last couple of years. I don't water older shrubs, grass, or trees. I figure they have deeper roots and can survive on rainfall.

My original soil is very dense clay. It is hard, impenetrable, and brick-like when it's dry. I have mulch on everything, but the newly planted things are still wilting in this heat. I am having trouble keeping everything watered.

Keep in mind that it's been EXTREMELY dry and it's going to take a lot of slow dripping water to soften and penetrate. If the ground is already dry and hardened, water from a fast-flowing hose will just run off. Hopefully the rain this weekend will be slow and steady and help us all out.

And yes, the newly planted things have been suffering a bit this week. New babies always have trouble when it's 80 and sunny. I ususally try to plant in the evening so they have the night to settle in before the brutal heat of the day.

It depends on the water pressure that is feeding the soaker hose. I used one of my narrower hoses to feed a soaker hose, and didn't get much. Then I connectedt it to a large hose and it did a great job.

I've had good success with soaker hoses last year in a couple of beds. So this year I'm in the process of running soaker hoses in all my beds as it seems to be much more efficient with water and time. Some areas I let it run for a good hour and others only a few minutes depending on how hard the soil is. Mulching over them will help retain the moisture in the soil and I've found it also protects your hoses somewhat from the sun beating down on them and damaging them over time. I also advise draining & storing your soaker hoses in the winter as opposed to leaving them out in the garden when not in use. They will degrade much faster than regular hoses if left out in blazing sunlight even in colder months.

Squirrellypete

You may be surprised at the small amount of water that is necessary to apply the equivalent of one inch of rainfall to an area with a soaker hose. The recommended spacing between hoses is 2' and if you use a 100' hose (maximum feasable length because of the necessary low pressure, hence volume), you will be watering a 200 ft² area. That will require only about 125 gal. to achieve the 1" application rate.
I have about 1000 ft. of soakers installed in areas where my overhead sprinkler would waste a lot of water. Also have some reserve hoses to water critical areas when the dew point is very low and evaporation rate becomes a problem with the overhead system.
Meauring the rate of flow is the only way to know how many GPH you are applying with a hose. I would expect each one will be different.
Rb