1/2 vs 3/4 outdoor frost free sillcock

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by mjm, Jun 17, 2011.

  1. mjm

    mjm New Member

    Messages:
    11
    Location:
    Alberta
    Hi,
    Have a question I'm hoping to get some enlightenment on.

    I currently have a 3/4 line going to my outside faucet, that needs replacing due to the fact that the cartridge in the shutoff valve going to it inside, is pretty much disentegrated, and the valve outside split over the winter.

    So the supply line is 3/4 and it goes into a 3/4 valve outside that then branches into 2 other lines(valves). 1 for an everyday 1/2 garden hose, but the other line feeds a 3/4 underground sprinkler system. The sprinkler system is not big, 3 legs with about 3 - 4 sprinkler heads on each. All of the line outside is soldered copper, except for the black tubing that feeds into the underground sprinkler manifold.

    So I want to replace with a frost free unit. 3/4 are just not all that available and I finally found one at a plumbing supply place, but I am starting to wonder about the whole setup. I don't think there is really going to be that much difference in water flow compared to a 1/2, by looking at the inside of this. I can also buy a fairly good 1/2 one anywhere, where as this 3/4 one did not come with the pressure valve on top or the plastic gasket to mount it on an angle, so I'm kind of wondering about reliability and then replacing it up the road.

    So wondering if any comments on whether I should stick with the 3/4" setup or change everything to 1/2"

    Thanks
  2. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    My first question is do you have a backflow device on the line to the sprinkler?
    I do not think you would notice the volume change that much if you went to 1/2".
  3. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,971
    Location:
    NW Ontario, Canada
    Most frost-free units are only frost-free if there is nothing attached to the end of them so that they can drain. If you mount a shutoff on the interior and properly drain the exterior portion, it too is frost-free. You can also buy insulated protectors to slip over them.
  4. mjm

    mjm New Member

    Messages:
    11
    Location:
    Alberta
    backflow device, I am not familiar with, so I guess the answer is no.

    I think what you'e saying is I could just stick with what I have and it would accomplish the same thing as the frost free. that's right, but I have to replace the shutoff inside and the main sillcock outside, so I might as well put in a frost free anyways, since it has to be replaced. Just wondering about the 1/2 vs 3/4
  5. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    A backflow device prevents contaminated water from being siphoned back into your potable water.Like a sprinkler,if you turn off your main and drain the system you have the possability pull contaminated water it to the water you drink,cook and bath in.
    Google back flow preventers it will tell you more.
  6. mjm

    mjm New Member

    Messages:
    11
    Location:
    Alberta
    wouldn't just shutting off the tap outside prevent backflow from the sprinkler system or garden hose. I can't see doing any work that would create a backflow situation while the valve going to either would be open.
  7. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    Yes that is true.It just that it is required on hose faucets here and is to protect you and your family.Just in case.
    But should be ok going to 1/2"
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,995
    Location:
    New England
    Backflow can happen if there is a hiccup in the supply pressure where the hose that is sitting in a puddle then sucks up insecticide, fertillizer, dog poop, etc...they are REQUIRED, not optional, as they protect not only your house, but the whole supply network.

    The internal port may not be that much different, but assuming they are proportional, a 3/4" pipe can flow about twice the volume of a 1/2" pipe. Since you want good flow for your sprinklers, I think you should stay with a 3/4" valve.

    There are a few companies that make a frost-free silcock that drains (and maintains the frost free aspect) even if you leave a hose on. Check out www.woodfordmfg.com.
  9. mjm

    mjm New Member

    Messages:
    11
    Location:
    Alberta
    Have to admit I am not too familiar with the backflow situation, but it is obviously a subject or we wouldn't be talking about it. I will have to look a bit closer, google shows it in industrial situations but not so much residential.

    3/4 ff sillcocks are hard to find here.
  10. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    This will work just fine.

    Attached Files:

  11. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Explain how the insulated cover would do any good?
  12. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,971
    Location:
    NW Ontario, Canada
    First, it forces you to remove the hose so that the bib can drain. It also has a foam gasket to reduce air infiltration. Lastly, it is insulated so it keeps a small amount of heat in.
  13. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,347
    Location:
    Yakima WA
    A note to MJM. The picture of the valve cwhyu2 post is an excellent example of a back flow device on a sillcock. You can quickly identify them by the cap on the top. That's the backflow part. As you know, the frost free part is on the inside end of the fitting. But, always remember the frost free is defeated if you leave a hose connected in freezing weather. I learned this the hard way several years ago.
  14. dlarrivee

    dlarrivee New Member

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    1,172
    Location:
    Canada
    Where does the heat come from?
  15. mjm

    mjm New Member

    Messages:
    11
    Location:
    Alberta
    I found this which explained it all to me.

    http://www.structuretech1.com/blog/category/vacuum-breaker/

    I thought the "vaccum breaker" on the top of the sillcock was a pressure relief thing and in conversation with someone they even referred to theirs as the same. Pretty sure the guy at HD even said the same when I asked. I don't think this is a very common topic here in Canada.
    So, having seen the pictures in this article, definitely the 3/4 one I bought has no vacuum breaker built in.
    So that leaves me with 3 choices.
    Go pretty much anywhere and pick up a decent 1/2 " one.
    Keep searching for a 3/4 " one, which is proving, pretty tough.
    Install the 3/4 " one I got and replace it when I can finally find a decent one, or order one I guess.
  16. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    If you install the one you have,you can put a vacuum breaker on it.
    You can get them at a plumbing supply and mabey a big box store.
    Or from the web site you posted.
    It attaches right on the hose connector.

    [​IMG]

    [​IMG]
    Last edited by a moderator: Jun 18, 2011
  17. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,615
    Location:
    Cave Creek, Arizona
    The only difference between a 1/2" and a 3/4" one is the pipe thread and some come with a 1/2" female-3/4" male thread so they can go either way. The only thing that MIGHT affect the flow is the size AND length of the pipe feeding it.
  18. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,971
    Location:
    NW Ontario, Canada
    I think it is a bit of a misnomer to call them backflow preventers. They are an anti-siphoning device, not a checkvalve. Picture a couple hundred feet of garden hose that has a bit of stretch to it. It acts much like an expansion tank would to store water and this water can flow in either direction as the pressure varies. Most garden hoses are not approved for potable water and the water stored in the hose at the highest pressure will reverse flow back into the house when the pressure drops.
  19. mjm

    mjm New Member

    Messages:
    11
    Location:
    Alberta
    I was just looking at mine more closely and that is exactly what it is 3/4" male x 1/2" female. I am starting to think that as far as frost free sillcocks are concerned I am looking at 1/2" if that is what I want. Or I forget about FF and go with my own soldered setup and get the 3/4. The size of the existiing pipe is 3/4 and it is about 15'. I'm not sure anymore this hassle of trying to accomplish staying with 3/4 is worth it. I may go with downsizing the feed to 1/2 for a couple of feet before the FF unit goes in.

    Once again, my intentions of just heading to HD and buying an off the shelf product, a 3/4 x 3/4 x 1/2 T and some fittings has turned into calling a bunch of plumbing supply stores and scouring the internets and not getting it done in a timely fashion
    Last edited: Jun 18, 2011
  20. mjm

    mjm New Member

    Messages:
    11
    Location:
    Alberta
    I still don't see this being an easy thing to have happen when the outdoor valve would be closed unless it is being used. But like I said it is obviously a concern or there wouldn't be any backflow/anti vacuum devices in stores. I just don't think the odds of it happening are high.

    Not that I don't believe you, I'm just having a hard time wrapping my head around it.
    Last edited: Jun 18, 2011
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