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GOGAYIccspoonts

Unregistered

1

Friday, May 18th 2018, 6:49am

Feed a Zone with 2 water sources

I have a rainwater tank and pump I want to use to water my existing flowerbed/garden zone on my system. My plan is to add a valve at the end of the zone that is fed with my rainwater source. This will in effect feed the zone from one end with a valve from the city water and the other end with a valve from the rainwater. Here is my question that goes beyond my understanding. When feeding the zone from one end will the water push through the valve on the other end that is not active? Do I need to do anything after putting the new valve on the end of the run? I dont understand enough how the valves are made to know if this will be a problem.

Wet_Boots

Supreme Member

Posts: 5,257

Location: Metro NYC

2

Friday, May 18th 2018, 10:32am

You are describing the kind of plumbing that can get your certificate of occupancy revoked.

A more practical application of your idea is look at the system as rainwater only, and to add a float switch to your storage tank. The float switch senses when the supply of stored rainwater is low, and triggers an inflow of city water to bring the tank level up to operational. That city water can flow through a simple vacuum breaker, to isolate the supply from the rainwater tank.

While your original idea could be realized in some parts of the country, by adding an RPZ backflow preventer to the city supply, said RPZ costs hundreds of dollars, and has a pressure loss that can kill the system performance. Much more certain is to function with the rainwater source, and to supplement the rainwater supply with some city water poured into the tank.

GOGAYIccspoonts

Unregistered

3

Friday, May 18th 2018, 10:54am

we already have a backflow preventer in place at the start of the system as to code in my area so thats not an issue for me. What I need to know is if my pump will push water backward through the city water side zone valve or if I need to put in a check valve.

Wet_Boots

Supreme Member

Posts: 5,257

Location: Metro NYC

4

Saturday, May 19th 2018, 8:25am

we already have a backflow preventer in place at the start of the system as to code in my area so thats not an issue for me.
You are misinformed. A "backflow preventer" is not proof against every possible problem. Pumping outdoor water into a sprinkler system connected to city water is a special case. Your local authorities can prohibit this practice out of hand, and all you can say about it is "Yes sir."

Even where it is permitted, the city water must be protected with an RPZ. Nothing less will do, and the RPZ is subject to annual testing requirements by a licensed backflow tester who files paperwork with the government department keeping track of these things.

People who do what you are describing can find out the hard way that local authorities can shut off the city water supply, at which point the home is legally uninhabitable and subject to being condemned and padlocked. You are owed no consideration, legally or otherwise, when it is discovered you are putting potable water in danger. Nothing you want here is worth picking a fight with authorities who can give you an extremely bad time.

More than anything else, it is the money aspect of RPZ backflow protection, its purchase cost, its maintenance cost, and its impact on system performance (on account of an RPZ subtracting at least 10 psi from the supply pressure) that make a dual-feed sprinkler system a poor idea. It is so much easier to pour city water into your rainwater tank, and pump it to the sprinklers. No RPZ. No required inspections and reports.

If this all seems fantastic to you, remember that city water supplies are now a matter of interest to the Department of Homeland Security. Feel free to contact them about your intentions.

BackflowInspector

Supreme Member

Posts: 482

Location: Houston, Texas

5

Monday, June 4th 2018, 4:18am

Wet Boots
Dropping the knowledge.

You hit the bulls eye.

Nice.

:thumbsup:
:thumbup: :thumbsup:
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