Question
we are considering putting in a drip irrigation system for our two flower beds.

I have two questions

the first is probably real easy: we today have an automatic timer which open and closes a garden sprikler. When the water turns off it hammers the plumming (you hear the 'bang'). What would we need to buy to prevent this ? would a back flow valve solve the problem ?

my second question is a bit more techical:
we have densly planted flower beds with plants which are sensitive to getting foilage wet. We want to put in drip irrigation (instead of soaker hoses) and misters are really not practical for us for above reason.

The main feed will be 0.7 OD poly tubing (similar to 1/2" poly tubes) with two 1/2" lead tubes going into each bed. From these 1/2" lead tubes we plan to run a number (probably 2 in each bed) of 1/4" dripper tubes (which is simply tubes with drippers premanufactured instead of you having to buy the drippers and put them in manually).

Water flow is maximum 220 gph at 25 psi regulated pressure. e.g. relatively low pressure.

We can get 1/4" tubers with the drippers spaced either every 12" or 6".

What would be the best spacing to ensure uniform evenly coverage of the entire area ? Is it necerssary to buy the 6" spacing or should 12" spacing do it ?

Offhand prefer 12" spacing since our plants are planted about every 10-12" and this way we can place the drippers between each plant..
my question is if it will be enough or we should opt for the 6" spacers ?

(the two flower beds are relatively small: 10'x2' each).

Thanks in advance
Kenneth

Answer
Kenneth,

The answer to question one is no. A backflow preventer only keeps water from being forced from your lawn or garden, through the valve, back into your home plumbing. Check with a local plumber, I'm sure that they can install a device to reduce or prevent water hammer.  

Question two is really up to you. I would opt for the six inch spacing because of the low flow volume of 1/4 inch tubing. Most of your water is going to work it's way down faster than it spreads outward. Mulching will help this, and you say that plant spacing is about 12 inches. That certainly lends itself to the 12" tubing. I just feel that the 6" tubing will give better performance in the long run. (Don't forget the mulch!)

Larry