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Will some backflow valves reduce City's water psi lower than others?

wickware

Unregistered

1

Wednesday, June 18th 2008, 4:22pm

Will some backflow valves reduce City's water psi lower than others?

Will some backflow valves reduce City's water psi lower than others? If so, what backflow valve will reduce the psi the least. I am trying to run 6 manual stations (3 at a time, 3 front or 3 rear) from a 30 + year old system. 3 fronts or 3 rear satations runs fine without a backflow valve. Each station has one rotary head and 2-3 popups, 3/4" city's main line with 3/4" schedule 40 PVC serving all stations. A faucet is at each station and psi measures 50-60 psi.

Will a Brass Vacuum Break (above my lowest head) be my best option with the least reduction in psi (if a backflow will not worlk?

Thanks for your info.

HooKooDooKu

Supreme Member

Posts: 683

2

Thursday, June 19th 2008, 7:29am

Every backflow is different, and even the same backflow can be significantly different depending upon the flow rate.

As a weird example, an RPZ (which will kill psi the most) can have LESS psi loss at a higher flow rate.

So the only way to find out exactly how much pressure loss you can expect, you have to know your flow rate and what pipe size you want on the backflow and then look at manufacturer's spec's like this... http://www.febcoonline.com/pdf/ss765.pdf (2nd page shows pressure losses v. flow rate for different sized febco PVB).

Otherwise, the only gross statements that can be made are that PVB and DCA will have something in the neighborhood of 5psi loss while RPZ will have something around 12-16psi loss.

Wet_Boots

Supreme Member

Posts: 4,102

Location: Metro NYC

3

Thursday, June 19th 2008, 7:53am

Define "manual station" - on flat ground, the simplest way to get backflow prevention is to use individual antisyphon control valves for each zone (the valve is higher than any pipe or head it feeds)

wickware

Unregistered

4

Thursday, June 19th 2008, 9:04am

Will some backflow valves reduce City's water psi lower than others?

My "manual station" is where I turn on a gate or ball valve to supply water to the 3-4 heads. I feel this is a "zone" in correct terminology.

I am on flat ground and I will use individual in-line valves if needed. This will create a larger winterizing job if 6 vs 1 valves are installed above my highest head. I would like to use a brass antisyphon valve at one location separated from the main with a ball or gate valve that will drain.

wickware

Unregistered

5

Sunday, June 29th 2008, 12:33pm

Will some backflow valves reduce City's water psi lower than others?

Hello Again!

1. Are Brass Atmospheric Vavuum Breaks mounted 12" above the highest head just as safe as Double Stop Valves?

2. Is using Flex PVC a better method of not reducing pressure/flow vs 6 elbows at my farthest head from main/zone?

Thanks for your info and comments.

Joe

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