Yard hydrant leaks underground

[Brad6006]

Help please.
So my well pump is in my basement, it runs my geothermal heat pump and 3 yard hydrants. I'm in South Dakota. So middle of last winter, my yard hydrant (Merrill Anyflow) started bubbling water up from underground when the handle was lowered, in the off position. My hydrants have 6 ft buried, 2 ft exposed above ground, so well below the frost line. For 20 years I've lived here and not had problems with freezing in the winter. I use the hydrants daily summer and winter to water animals on the farm.
I called Merrill and talked to tech department and they couldnt figure out why the hydrant would leak when the water was turned off, so they said Id have to dig it up as the leak was probably at or near the elbow. I have good pressure at the hydrant, when the handle was raised in the on position, my pressure was as good as ever, but when the handle was in the off position, water would bubble up from underground. I tried repositioning adjustment nuts both directions. There never was water leaking from the nozzle or any fittings above ground.
So, this week I had a guy out and dug a hole and replaced the hydrant and it works fine now. BUT, my yard hydrant by the garden is now doing the same thing. After 15 minutes with the well on, I have a puddle of water near the hydrant, and the handle is in the off position. So same as the other hydrant, it's leaking below ground with handle in the off position.
Any ideas what may be wrong? Is this a crazy coincidence that both hydrants, roughly 5 years old, would leak below ground? Could my pressure switch on my well pump be set too high, or too much water pressure in my pressure tank that's pushing too much water pressure to my hydrants? Is it possible the drain ports are somehow damaged and allow water to flow out?
I find it hard to believe Merrill hasn't heard of this problem before, yet I have 2 hydrants doing it.
I inspected the hydrant we dug up yesterday and the plastic pipe at the connection to the bottom of the hydrant drain valve looked good, tight, and undamaged, not sure where it would have been leaking
Like I mentioned, I've been here over 20 years and never had problems like this.
I hope someone may have experienced this and be able to give me some advice.

 

[John Gayewski]

If it's anything like my girlfriend's farm (out in the sticks) whomever built it used the cheapest easiest methods. As soon as I fix one leak another one pops up. It's the nature of a system worth poor fitting and pipe systems. Actually really any system. A lot of times the pressure is being relieved by a leak so when you fix it the next weak point goes.

 

[Sponsor]

 

[Tuttles Revenge]

I've got a couple hydrants that are likely going on 20yrs and haven't had that issue that I know of... they are sort of placed in a swamp so maybe I would never know.

But valves wear out, especially if used every day. I've never had the opportunity to repair one but it seems there would be replacement parts for them... Just looked up parts and it appears there's a rubber plunger that fills a hole at the base. Probably at 20yrs old it can hold back 90% of the pressure thrown at it.

 

[Valveman]

Frost free hydrants don't last long for me either. The valve in the bottom that closes off the main line and opens the drain port usually fails. I have just got use to replacing them.

 

[Brad6006]

Frost free hydrants don't last long for me either. The valve in the bottom that closes off the main line and opens the drain port usually fails. I have just got use to replacing them.

That sounds like the most likely problem to me. I wondered if the frost free port could allow water to escape when the handle is in the off position. I pulled the stem and put a rebuild kit in, replacing all the guts. I didnt think that would make any difference but it was worth a try for the $20 kit. And if the seal or plungers were bad, Id assume the leak wouldnt be when the handle is in the off position. If the seals were bad, I'd assume water would be leaking up the pipe and out the nozzle.

 

[Jeff H Young]

Being from warm southern Ca . I've never had one apart but if it leaks a small amount when off the water will come out the waste holes and eventually flood area I would expect. So It sounds like a rebuild is in order .

 

[Reach4]

https://www.merrillmfg.com/blogs/videos/how-to has several videos on the repairs.

 

[Brad6006]

https://www.merrillmfg.com/blogs/videos/how-to has several videos on the repairs.

Yup watched those a month ago. Called their tech department as well. They said if its leaking with the water off, the problem is not in their hydrant. I have a sneaking suspicion water is coming out the drain hole when the handle is in the off position. I'm gonna rig the one I dug up to a garden hose attachment and see if I'm correct.
Since the pvc pipe underground isnt leaking after replacing the first one, I figure it's got to be coming from the frost free drain. Maybe it has debris/sand in it and is allowing water to pass by?
I'm also gonna try a suction test on the 2nd bad one that's still buried, that should tell me if its the drain I would think.

 

[Reach4]

Did you try replacing the plunger? That gets done from the top, as I understand it. Plunger is the part with the spring in https://www.merrillmfg.com/collecti...-parts-kit-for-high-capacity-any-flow-hydrant


"I'm also gonna try a suction test on the 2nd bad one that's still buried, that should tell me if its the drain I would think."
Wouldn't a working brand new yard hydrant also not hold a vacuum? And I don't mean just because of the vacuum breaker if present. The riser drains of water when the hydrant is off. So unless the drain at the bottom was below the ground water level, I would think air could suck in that way, depending on the permeability of the soil.

 

[Jeff H Young]

Yup watched those a month ago. Called their tech department as well. They said if its leaking with the water off, the problem is not in their hydrant. I have a sneaking suspicion water is coming out the drain hole when the handle is in the off position. I'm gonna rig the one I dug up to a garden hose attachment and see if I'm correct.
Since the pvc pipe underground isnt leaking after replacing the first one, I figure it's got to be coming from the frost free drain. Maybe it has debris/sand in it and is allowing water to pass by?
I'm also gonna try a suction test on the 2nd bad one that's still buried, that should tell me if its the drain I would think.

I think thats What I suspected when commenting in post number 6. water leaking past and coming out the drain hole .
im uncertain exactly the cause The hydrant removed should offer oppotunity to figure out possible repair options.
if its unserviceable from the top dig it up repair it or replace

 

[John Gayewski]

When these break, which they do all of the time, I install them so they can be replaced from above. I do this by feeding the new hydrant through a PVC sleeve and using insulation to make up the difference in diameter. This allows them to be unscrewed from above and replaced later.

 

[Valveman]

When these break, which they do all of the time, I install them so they can be replaced from above. I do this by feeding the new hydrant through a PVC sleeve and using insulation to make up the difference in diameter. This allows them to be unscrewed from above and replaced later.

That's a good idea. I don't think they will be quite as "freeze proof" that way, but would be much easier to replace. And yes they need replacing all the time as the bad plunger can make them leak out the faucet or out the drain port.

 

[John Gayewski]

That's a good idea. I don't think they will be quite as "freeze proof" that way, but would be much easier to replace. And yes they need replacing all the time as the bad plunger can make them leak out the faucet or out the drain port.

I've had two installed for three years in this way. They survived the polar vortex and a couple other historic cold snaps. I was a little worried about them, but it's been working.

 

[Tuttles Revenge]

I've had two installed for three years in this way. They survived the polar vortex and a couple other historic cold snaps. I was a little worried about them, but it's been working.

How do you secure the Female threads in the ground? When I've done them, I've always used a series of street 90s to create a swivel in case they get bumped, the threads can move along with and not break. But besides my own yard I don't know that its ever been necessary to do that in that way.

 

[Jeff H Young]

If you had the last 2 foot running horizontal in galvie with a 90 looking up it might be secure for unscrewing but plastic might /likely snap if not having a few feet of something stronger

 

[John Gayewski]

How do you secure the Female threads in the ground? When I've done them, I've always used a series of street 90s to create a swivel in case they get bumped, the threads can move along with and not break. But besides my own yard I don't know that its ever been necessary to do that in that way.

I actually don't remember what's under there. If my memory is correct there's a brass tee looking up as they are in series. I haven't had the pleasure of replacing one yet.

At the time I figured this would give me the best chance of changing them without digging, but if I can't I'm not out anything really.

 

[Lightninboy]

How did it turn out? I've got a somewhat similar situation.