Anti-Siphon Frost Free Sillcock won't let pipe drain?

Hello all. I have a question about a problem I'm trying to prevent from happening again.

Here's my background information:
A basement water pipe that leads to a frost-free sillock froze and burst. It's a walkout basement and the pipe runs from the sillock up the interior basement wall to the ceiling joists. There is a cutoff valve in the ceiling joist. (which I unfortunately neglected to close this winter) The basement was finished into living space a few years ago. The insurance adjuster determined the root cause of the problem to be the fact that the insulation was placed on the wrong side of the pipe when the basement was finished. That is, the pipe was located on the cold side of the insulation instead of the heated space side. (Closing the additional cutoff valve would have been a good idea too. )

What I've done:

1. Upgraded the leaking cutoff valve with a ball-valve.
2. Replaced the frost free sillcock hose bib with a new unit, which is apparently also anti-siphon. (The old unit was getting difficult to turn) My original sillcock was not anti-siphon. The new (B&K Mueller) one is anti-siphon. (Apparently it's now required).

My question:

I've noticed that even if I turn off the shutoff valve in the ceiling joists, the anti-siphon "feature" of the sillcock won't allow the wall pipe to drain. It drains the sillcock, but the remaining wall pipe does not drain. This seems like a problem. Is this normal? It seems that this anti-siphon "upgrade" may be worse in my particular case. Is there something else that I should do to drain the wall pipe?

Thanks for any help!


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Let's see if I have followed your tale of woe correctly. The supply pipe on the inside of the house to which the anti siphon frost free valve is attached must be protected from freezing. It does not drain. The anti siphon frost free valve comes from the above freezing area inside the house to the outside and does drain. The actual shut off portion of this valve is located on the inside end of the tube which is usually 12" or more long. In order for it to drain, two things are important. First, there must be a slight tilt to the outside so that water will not remain in the tube between the shut off and the outside. Second, you must never leave a hose connected to the valve during freezing weather. If you do, the tube will not drain and the water will freeze and split the tube. The water will still be turned off and there will be no leak until you turn the valve back on. The anti siphon feature simple prevents the water in the hose from siphoning back into you house water system. I do not follow your reasoning for having a ball valve involved.

Thanks for the reply. You correctly summarized the problem when you said "The supply pipe on the inside of the house to which the anti siphon frost free valve is attached must be protected from freezing." The frost free antisiphon valve (10" long) is tilted properly and drains. However the interior supply pipe may still freeze because the small area behind the interior wall apparently gets cold enough to freeze. The cutoff valve installed in the overhead area was simply a valve to shutoff water to the supply pipe to the sillcock in winter. Previously, the supply pipe would drain, now it cannot becuase the sillcock is anti-siphon.

I'm attaching a picture which shows what I'm describing. If you look closely, you'll see the shutoff valve overhead that I mentioned.

*bump*

I'm still trying to figure out if that anti-siphon is the reason that the supply pipe will not drain as part of my winterization. Before I had an anti-siphon sillcock, the supply pipe could drain after I closed a supply pipe cutoff valve and opened the sillcock valve.

Your thoughts are appreciated.

most frost proof hose faucets are spring loaded to allow water drain from the sill cock,to prevent the pipe from freezing.That will keep the water from
draining out of your feed even with ball valve shut off.

pipe

The water in the pipe is being retained by a vacuum. There is NO WAY, air can enter the pipe through the hose faucet to break the vacuum, whether it has a vacuum breaker or not, because its internal opening is too small to allow air IN and water OUT at the same time. The only way to drain it is to provide a way for air to enter AT, or NEAR, the shutoff valve.

Thanks for the replies. I opened a bleeder valve near the supply cutoff to allow air in, but nothing drained out of the supply pipe through the faucet. I tried to lightly blow air through another frost-free faucet and found that it blocks air unless I blow real hard and then it pops open. I now realize that without pressure, the sillcock will not allow water to pass through it.

It looks like there isn't much I can do to drain the supply pipe without some excessive measures like adding a blowout plug fitting.

It sounds like the frost free sillcock you have uses a spring loaded check valve for backflow protection at the inlet connection. When you shut off the sillcock, the remaining water contained in the section of pipe between your ball valve and the sillcock inlet does not create enough pressure to overcome the spring loaded check valve in the sillcock inlet and drain that section of pipe.

faucet

Backflow protection has ALWAYS been a requirement, but a vacuum breaker faucet is not the only way to provide it. A vacuum breaker screwed to the end of the valve is the common way to do it. With those, you can "pull" on the center of the VB and allow the water to drain out.

hj said:

Backflow protection has ALWAYS been a requirement, but a vacuum breaker faucet is not the only way to provide it. A vacuum breaker screwed to the end of the valve is the common way to do it. With those, you can "pull" on the center of the VB and allow the water to drain out.

Click to expand...

There is always some manner to get the vac breaker to allow draining whether it is something you push or pull in the center of the outlet or, a pulldown ring on the outside. you might have to find the instructions for your make and model if it is not evident...

I'm no plumber but where I live (and in my basement) water pipes along an external wall above the frostline must be kept a minimum of 6 inches inside the wall by code.

Your pipe seems to be sitting within 4 inch studs.

Does this rule not apply to garden faucets? Or is it just a local thing?

It depends a lot on location however the fact that it froze speaks volumes...