Faulty Check Valve?

[joesandy1822]

I think I have a problem. Shouldn't a check valve prevent backflow of ALL water? We installed our pond a couple months ago, and I never even thought of this until now. But every time I turn off the pump to clean out the skimmer, the filterfalls empties about 3/4 of its water. So I hurry to do it as quickly as possible to preserve the bacteria. But I am thinking this is just not right. There should be no water loss out of the falls if the check valve is working properly, correct? The check valve is connected to the pump, which is in the skimmer.

Thanks for any help.

Sandy

 

[dieselplower]

I would expect a properly installed check valve would prevent backflow yes.

 

[DrCase]

Like any valve any thing can get hung in it too keep it from closing positive

 

[Mmathis]

Is it set up going in the correct direction of flow?

 

[joesandy1822]

Is it set up going in the correct direction of flow?

Yep, the falls work fine so it must be installed the right way. I suspect there might just be a little piece of something in there keeping it from completely shutting, or maybe I don't have one of the hose clamps completely tightened. I have noticed that when the pump is off, there is a little "pulsing" type thing going on. Like about every 3 seconds, the pipe pulses or jerks. I'm thinking during the little jerk movement, a small amount of water is escaping the check valve. It's not a big deal, so I might just wait until I put the pond to bed for winter to take a closer look. I rarely have to shut off the pump, so unless we have a power outage, I think we'll be good.

 

[addy1]

Some of the check valves are fussy about being straight up and down, not laying at a angle. I have one on our stream pump, it does ok at a slight angle, but shallower angle it fails. Hope that makes sense, the pvc pipe I had to make sure it was going as straight as possible down the side of the pond in the water.

 

[Dave 54]

From time to time when I flush my filters I get things hung up on it and it doesnt give a propper seal , your going to have to check if you have the same problem you can try upening it up again to see if you can flush it through ours normally clears doing this.
It's amazing just how much water you can loose from just a small gap .

rgrds

Dave

 

[Waterbug]

I have noticed that when the pump is off, there is a little "pulsing" type thing going on. Like about every 3 seconds, the pipe pulses or jerks. I'm thinking during the little jerk movement, a small amount of water is escaping the check valve.

That explains the problem. It also shows that the check valve is actually sealing perfectly.

This is a little tricky to explain so I'll make a an example that's probably simpler than your pipe layout. Say you have a vertical, or somewhat vertical, pipe going from your pump up to the falls and there's a check valve in that pipe. When the pump turns off the weight of the water in the falls starts flowing backwards and the check valve closes. This is how you expect it to work, and this is what is happening.

What you probably aren't expecting is for the check valve to open back up every few seconds.

You probably think that water below the check valve falls out of the pipe when the pump is turned off? It isn't in your case. The check valve is sealing so well the water below the check gets stuck exactly the same way as when you place your finger on the end of a straw and pull the straw out of a glass of water. The water inside the straw stays in the straw.

Slowly a bit of water at the very bottom of the pipe will fall out of the pipe, which sucks some air into the pipe. That air moves up thru the stuck water until it hits the check valve, opens the flap and water from above, in the falls, flows past the flap to replace the air void. Pressures go back to "normal" and the flap seals again. This repeats over and over and slowly the falls will drain. Depending on your set up you might see a big burst of air bubbles come into your falls when this "jerking" action takes place.

Exact pipe layout can make this all worst or non-existent

The problem and fix is hard to guess without seeing the layout. So I'll guess. The check valve is suppose to be installed very close to the "open end" which normally would be right next to the pump's output. That reduces the amount of stuck water which reduces the problem pressure inside the pipe.

If you can't move the check valve you can vent it by adding a tee as close to the bottom of the valve as possible and running pipe off the tee vertically to a point above the waterfall's highest point. If that vertical pipe can't be hidden you can use a shorter length and add an air admittance valves. They're pretty cheap, $15-20. That will allow water in the pipe below the check to drain out as soon as the pump is turned off and the check will remain closed.

The vent pipe does not have to be as large as the water pipe, however it should be. A smaller pipe will create some jerking, but it will be only for a second or two.

If none of those fixes can be made I would consider removing the check valve entirely because it's not doing what it's suppose to do and the jerking can create a leak in a fitting over time.

Yep, the falls work fine so it must be installed the right way.

That a check valve works properly when the pump is on does not indicate that the check valve is installed correctly. These can be installed backwards and still "work" when the pump is on. Depends on the entire system, not just the right direction. So I'd still double check, no pun intended, the direction of the valve. Probably OK, but 2 seconds to verify.

 

[Shelly]

My pond has a few Spears pvc swing-type check valves. The installation app note says these particular valves are designed for horizontal installations, but may be installed in up-flow only vertical position.

Of course the flow direction must be respected regardless of the installation orientation, horizontal or vertical. A swing check valve will also have top indicator (molded in the plastic) which also must be respected when mounted horizontally.

 

[Waterbug]

Following the directions for vertical vs horizontal and direction is required. But that alone does not guarantee it's installed correctly. There's a bunch of ways to still mess it up. The directions can't describe all the possible ways it can be messed up. It's the responsibility of the installer to design a system in which a check valve can function.

 

[joesandy1822]

That explains the problem. It also shows that the check valve is actually sealing perfectly.

This is a little tricky to explain so I'll make a an example that's probably simpler than your pipe layout. Say you have a vertical, or somewhat vertical, pipe going from your pump up to the falls and there's a check valve in that pipe. When the pump turns off the weight of the water in the falls starts flowing backwards and the check valve closes. This is how you expect it to work, and this is what is happening.

What you probably aren't expecting is for the check valve to open back up every few seconds.

You probably think that water below the check valve falls out of the pipe when the pump is turned off? It isn't in your case. The check valve is sealing so well the water below the check gets stuck exactly the same way as when you place your finger on the end of a straw and pull the straw out of a glass of water. The water inside the straw stays in the straw.

Slowly a bit of water at the very bottom of the pipe will fall out of the pipe, which sucks some air into the pipe. That air moves up thru the stuck water until it hits the check valve, opens the flap and water from above, in the falls, flows past the flap to replace the air void. Pressures go back to "normal" and the flap seals again. This repeats over and over and slowly the falls will drain. Depending on your set up you might see a big burst of air bubbles come into your falls when this "jerking" action takes place.

Exact pipe layout can make this all worst or non-existent

The problem and fix is hard to guess without seeing the layout. So I'll guess. The check valve is suppose to be installed very close to the "open end" which normally would be right next to the pump's output. That reduces the amount of stuck water which reduces the problem pressure inside the pipe.

If you can't move the check valve you can vent it by adding a tee as close to the bottom of the valve as possible and running pipe off the tee vertically to a point above the waterfall's highest point. If that vertical pipe can't be hidden you can use a shorter length and add an air admittance valves. They're pretty cheap, $15-20. That will allow water in the pipe below the check to drain out as soon as the pump is turned off and the check will remain closed.

The vent pipe does not have to be as large as the water pipe, however it should be. A smaller pipe will create some jerking, but it will be only for a second or two.

If none of those fixes can be made I would consider removing the check valve entirely because it's not doing what it's suppose to do and the jerking can create a leak in a fitting over time.

That a check valve works properly when the pump is on does not indicate that the check valve is installed correctly. These can be installed backwards and still "work" when the pump is on. Depends on the entire system, not just the right direction. So I'd still double check, no pun intended, the direction of the valve. Probably OK, but 2 seconds to verify.

Thanks, Waterbug, for that thorough description. I'm glad you understood what was happening and could articulate it for others. I will just leave it as is. It's not that big of a deal. It is definitely installed correctly. My husband and I both double checked. It is only about 3" above the pump, inside the skimmer box. If it did create a leak, the leak will be inside the skimmer box, so that is not a problem. And if I remove it completely, then the whole falls will definitely drain each time the pump is off. The way it is now, it takes a good half hour for it to drain about 2/3 to 3/4. I typically can rinse the skimmer media within about 10 minutes, so it should be fine.

 

[DATTCOMM]

Sandy,

I'm about 6 weeks behind everyone else, but just joined the forum.

I have the exact same problem and it makes little sense to me since my check valve is installed directly out of the skimmer box water pump. Near my waterfall box, I installed a 2" cut-off valve on the inlet pipe. When I turn off the pump for cleaning, I close the valve and the water that usually pulses it's way down the pipe, through the check valve, and into my pond is immediately cut off. This way, I can take my time and clean the media and filters within the waterfall box. When done, I open the valve and turn on the power to the pump.

This solved my biggest problem, but I do face the same problem if we lose power. If I'm not home, I will find that my top waterfall box empties back into the pond. Quite a pain when that happens. I'm thinking of purchasing a cut/off valve that is controlled by 120VAC. I've seen them controlled by low voltage, but I really hate spending that kind of money when there should be a "no voltage" solution.