Question about Check Valves

[johnoburns]

I am curious if anyone uses or has used check valves in the aquarium setup. I think they could aid in some of the overflow problems people have.

In case you are unfamiliar with what a check valve is it restricts flow of water to one direction.

Here is more detailed information from wikiapedia.

A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. There are various types of check valves used in a wide variety of applications. Check valves are often part of common household items. Although they are available in a wide range of sizes and costs, many check valves are very small, simple, and/or cheap. Check valves work automatically and most are not controlled by a person or any external control; accordingly, most do not have any valve handle or stem. The bodies (external shells) of most check valves are made of plastic or metal.

Edited April 5, 2009 by austinaquaman

[caferacermike]

I'll try and help a touch as I am backflow certified, meaning I have the ability and engineering certification to legally test backflow preventers and check valves.

You can use them on your tank but I would not recommend it. With some very simple math you can easily design a sump large enough to hold any back siphoned water within it. The problem quickly arises when folks cheap out and buy a 20g sump for their 240g tank. I generally believe that your sump should at a minimum be 1/4th the size of your tank.

The problems with using check valves are numerous.

First they rob flow. You must have a high volume pump that can handle a little back pressure. If you plan to use a check valve you are limited to using a "swing check" only. Spring checks will rob your flow and will buzz constantly as they try to fight the pressure of the pump. A swing check may "clack" around as pressures fluctuate. If you buy a swing check, buy the clear one from Marine Depot. Also since they are extremely restrictive buy one that is one pipe size larger than the pipe it will connect to and bush it back down. This way the area through the throat will still be the same internal diameter as the pipe in the system.

Another huge problem I've seen dwells upon the fact that if you are relying upon a check valve, then it will fail you at some time. Think about all the tiny little creatures that we benefit from in our tanks. How many baby snails will be traveling within the piping? What happens when you lose power and a snail shell is caught in the clapper of the check valve? It will leak by. Another thing is that we add a lot of calcium to our tanks. Being that I've helped tear down close to 50 tanks over the past couple of years, I'll say that many of them had mineral deposits on the inside of the piping. This means that the sealing area of the check valve could easily become blocked with hard calcium deposits or other minerals. Again preventing a good seal and a leak back condition.

I've also encountered check valves that have frozen in place over time. Meaning that after a few years of not being serviced they won't close.

So with all of that in mind you might see why I say "just buy the right sized sump". I've never had a sump overflow once properly designed and set up.

[johnoburns]

I have to agree having a big sump is best, not just the over flow advantages. I'm looking into setting up a new tank right now and want a sump around 50% of the tank size.

I was just thinking about other ways to help people out with some flooding problems. I've come across a few threads with this happening. Some in apartments and some being out of town. The worst one I read was a second floor apt flooding and leaking in the apt downstairs.

Having a check valve fail would be the biggest issue, but you could do things to help with this. Putting two in series and/or replacing them somewhat regularly. For most of us replacing them seems like a big task, but for apartment dwellers who move and take the tank apart anyway this might be a good option.

Robbing the flow was something that I had thought about. I hadn't done any math on it, but realized there would be some loss there.

Edited April 5, 2009 by austinaquaman

[caferacermike]

Ah but for our second, third, and whatever floored reef keepers that choose not to have a large enough sump to catch their overflow get what they deserve. I know that is some harsh language and all but well........ It's true.

Even more so if you live in a second floor apartment. There is this weird little thing that some of us believe in called "responsibility". If you are living in a dwelling that you do not own and choose to have a tank, then it is your utmost responsibility to make absolutely sure that you will not do any damage to that place of residence, especially so if you might possibly cause harm, or injury, to another innocent person or being below you. I wouldn't shed a single tear for a thread from a second floor dweller that told a story about how their 240g tank was plumbed into a 20g sump and when they lost power, they drained 40g of water into the apartment below and that now the management is suing them for damages as well as the people below. If I lived below that person and they allowed their tank to overflow into my apartment, I'd be out for them. I'd have zero compassion for their loss or troubles.

I guess I'll sum it up like this and then not say anymore, we need to stop applying bandaids and quick fixes to our problems rather than treat the original source of the problem. Don't cry to us that your stand is to small to put a good sized sump within it, instead buy another stand. Don't rely upon a mechanical "gadget" as a mechanical device can fail. And then what? Are you really going to tell the Judge in your Civil Suit that you should not have to pay for the damages to the apartment and the other Tenants belongings because your "check valve" failed, thereby releasing you from fault?

[AlexKilpatrick]

I have had check valves (the clear ones) on several tanks and they have never failed. It is possible, but anything is possible. I like using the NASA approach of having multiple redundant failure prevention systems.

You don't have to have a huge sump -- you just need to make sure your return is high enough so that the reverse siphon does not involve a lot of water. That could be just the first inch or so of water in the tank.

I am interested in preventing floods, though. I am going to start a thread just about "flood" stories, so maybe people can learn from other's mistakes.

[prof]

The size of the sump is not nearly as important as the empty space in the sump. I start with a 4" calculation to determine the amount of extra space needed in a sump.

For example:

For a tank with a 48x24" foot print. Multiply by 4 to get 4608 cubic inches, divide by 231 to get gallons: 19.9 gallons. So, regardless of the height of the tank I want the sump to be able to catch an extra 20 gallons of water in an emergency. This means running a 40 gallon sump, half full.

Now, 4" is overkill. Properly designed overflows and returns should never siphon more than one inch of water in the case of a power outage but if you have a clogged siphon break and your return is 6" underwater....you will siphon 6" of water out of your tank. From the above example, that would put 30 gallons of water in the sump. I hope you have room

I like to split my return line so I have two siphon breaks on one return. Redundancy. Dual overflows are also great for the same reason.

In my opinion, check valves are a waste of money. It is much more likely that they will cause a problem then solve one.

A common thing that people forget is that the tank can easily overflow over the top instead of through the plumbing. On more than one occasion I have had algae build up or a rougue snail clog my overflow. When this happens the pump will run the sump dry and all of the water will exit the system over the top of the tank. Maintenance is the best method to prevent this. Make sure your plumbing stays clean, is easy to access for service, and has good screens to keep stray critters out of the lines. Cheap water sensor/alarms can be installed to alert you to water on the floor and even cut off a pump before it emptys your 50g sump on the floor. When possible, a catch basin around the entire stand or a floor drain are great things to have.

One design that I am beginning to use on sumps that I build is an extra catch bucket. It is easy to add 3-4 gallons of extra space in a side container that is designed to stay dry all of the time and only exist for the emergency. The rest of the time you can store supplies in it.

Remember that water seeks its own level, and in the aquarium hobby that is usually on the floor.

[subsea]

Excellant post with many relavant points. Stay away from check valves. The more stuff one accumulates the more stuff that can break down when you least expect it; KISS.

Pat