Full-Port Valves for Gravity-Fed Tanks/Cisterns
A full-port valve retains the full interior diameter of the pipeline it is connected to. This results in less reduction in flow (and less surface friction) than is caused by using standard valves, which have a smaller interior diameter than the incoming pipe.
Judge your rainwater system parts supplier or installer by what valves they offer
If you are looking into purchasing a rainwater tank, and you are planning to use the free power of gravity to move the water from the tank to your points of water use, then ask your parts supplier or installer if they can provide you with full-port valves.
If they DO offer full-port valves they are probably good.
If they do NOT offer full-port valves they probably are NOT good, and you should probably look for another parts supplier or installer.
They should be concerned with providing you with the parts and system that will work best for YOU, not the quickest/easiest thing for them to sell/install.
Some full-port valve options:
You can get full-port valves that are ball valves or not ball valves.
Full-port ball valves
These are great in warm climates, but they can rupture and leak if they freeze in cold climates. So make sure they are within properly insulated valve boxes in those freezing climates.
Stainless steel full-port ball valve
For a nice 3/4-inch diameter (optimal garden hose diameter for a gravity-fed system) full-port valve that works well on rainwater cisterns/tanks from which you irrigate your plants, see the link and images below:
Additional full-port ball valve options:
• Search “stainless steel full-port valve” on line.
Mueller (made in Italy and/or China)
Ball valve – full-port (Valvula de bola – con rosca – lumbrera completa)
3/4 inch 107-824
1 inch 107-405HC
Full-port valves that are NOT ball valves
Because these valves have a rubber seal they are a little more forgiving in freezing conditions than all-metal ball valves. Nonetheless, protect these valves from freezing by installing them in insulated valve boxes or covering them with insulation if there is a risk of freezing.
Full-port snub valves or bent nose garden valves are available.
I like to use a snub nose/bent nose with 1″ interior diameter base/inlet and a 3/4″ outlet with hose bib threads in gardens and landscapes. I then use the widest-diameter drinking-water-approved garden hoses I can get.
Arrowhead brass products (made in Los Angeles, CA, USA)
1 FIP x 3/4 hose, Hose – bent nose garden valve
930, 90043 00930
NOTE: In the same store (Bimsco hardware in Tucson) I have found this brand and model of valve made as both a full port valve, and a constricted valve, so always visually inspect all your valves to make sure they are what you want.
Mueller (made in China)
Bent nose garden valve (Salida inclinada valvula de jardin)
1 inch: 108-105
3/4 inch: 108-104
Legend is another brand, but more expensive.
Check out the video below comparing the water flow from a full-port valve versus a conventional constricted valve…
Ideal pipe diameter with home-scale, gravity-fed, rainwater harvesting tanks
I use either 1-inch (25-mm) or 3/4-inch (19-mm) interior diameter pipe (nothing smaller) to distribute rainwater from my tanks to their point of use when using the free power of gravity as my sole means of moving the water.
Hoses that maximize gravity-fed water flow
Make sure you also use 3/4-inch diameter garden hoses (NOT smaller diameter hoses) with gravity-fed systems to maintain the good flow the full-port valves give you.
More info on hoses here.