You are not logged in.




Thursday, May 17th 2012, 11:08am

backflow size question

I have a question that needs more experise than I have to answer. Installing RPZ between 3/4" county meter and 1" flex pipe to 1" valve tree that feeds 3/4" lines to 3/4" heads. I would like as much pressure as I can get to counter pressure loss from each zone. How much of a difference would a 1" RPZ make compared to a 3/4" RPZ. Buying Febco from sprinkler warehouse, fyi.
thanks for any help,


Supreme Member

Posts: 5,257

Location: Metro NYC


Thursday, May 17th 2012, 11:20am

Very little difference in pressure loss - maybe some difference in water velocity and relief valve 'spitting'


Supreme Member

Posts: 482

Location: Houston, Texas


Thursday, May 17th 2012, 5:58pm

First, I must give Props to all Mentors out there. You know who you are.

Second, In my Humble Opinion. You will probably lose between 8 and 12 lbs of pressure from the static pressure by using an RP. Hopefully you are starting with over 60 PSI.

What are you starting with?

As Stated Earlier not much difference between 3/4 and 1"!!!
8 to 12lbs is 8 to 12 lbs.

Hi.todd :thumbsup:
:thumbup: :thumbsup:
LI0006121, BPAT0011021, CI0009500


Supreme Member

Posts: 5,257

Location: Metro NYC


Friday, May 18th 2012, 8:02am

A good rule of thumb is to subtract 20 psi from the supply pressure when you have an RPZ. The resulting number will represent the best possible pressure at the heads, and that's before you include losses from the water running through the meter and supply line upstream of your system connection point.

Similar threads

Rate this thread