Hi GTN, Very good question. I'll bet your 3/4" spigot has a 1/2" copper line feeding it nor is a spigot 3/4" through out it's length. Smaller to bigger or vice versa doesn't matter. Size affects velocity at that change point, but very briefly. Length of pipe is what affects the system efficiency (loss of pressure) the most. Water flows faster through the smaller diameter pipe and when water velocity gets high enough turbulence in the pipe is reached and your friction loss per foot of pipe increases as well as noise. This friction loss robs you of pressure as the water travel along the system. Your system has high pressure so this not a big concern in your system. It becomes a design issue depending on where you reduce your pressure for your garden. 1 1/4" pipe was sized by a formula that calculates flow versus velocities in various size pipe. A standard design criteria for non-turbulent flow is less than 5 feet per second velocity(noise reduction). Using that criteria the 1 1/4" was acceptable, 3/4" would be less acceptable but still can be utilized with no real problems. It then becomes a cost issue. It makes no difference what size the source pipe is, but hooking up to your house affects the velocity of water traveling through your house pipes. If you turn on your hose, how noisy is the flow in your house? Does it affect the flow of other water using appliances being used at the same time? Turn on the washer, shower, kitchen faucet, etc an listen to the sounds of the water. If the answer is no to these questions your house water system doesn't pose a constriction to your garden water needs. The more items being run the noisier it gets. Did you ever call your builder and find out about the pressure regulator needed for your house water system? Just curious. GL. Aloha

A single 55 Gal watering system can be done between $100 - $200! (excluding pump)! Where as we collect water into a 1200 gallon underground tank and use a shallow well jet pump for distribution to our five water stations. Initial installation costs were over $4,000 in material and I did the work! And I'm considering adding an additional 800-1200 gallon tank! Your issues are going to be 1. What do your local building codes allow. 2. How large a tank can you use. 3. A large $$$ for you is going to be the size of the pump needed to pump water to the roof! Hope this helps........

Hi Ron - the issues I find with drip systems if buried is that the emitters are easily plugged/blocked by the soil and so quit working. So I'd sure work out a way to keep them on top of the soil as they are intended to be for best results. Otherwise you can end up with minimal if any water to the plants or only a couple getting all the water. Just lay the line aside when hilling the soil and then put it back in place. As for height when covering - minimal. Once the leaves develop low on the stem there will be no stolens formed at that level to make potatoes so you don't want to wait until the plants are more than 6-8" tall. So bury the bare stem as soon as it rises above the soil. The easiest approach I have found over the years is just to bury the whole plant except for the top few leaves as it grows. It pops right back up through the hilled soil and keep on growing. Dave

Oh I forgot to tell you that I broke one of the small pipes when I tried to remove this part. I was lucky that my neighbor (mechanic) helped me out for free to fix it for less than $10 by using 3/4" CPVC Thread Slip x Slip Coupling Fitting and JB Well. If these auto-drain parts break again, I will block those two pipe holes permanently. I don't mind to pay the cost of these two auto-drain parts; but I don't want to pay high water bill when they break down. Another thing after the fix, I noticed that the water came out from each sprinkler head stronger than before. Again thank you for your help.