Making Frag Plugs

I recently started to make my own frag plugs using a combination of sand and Portland cement. I figured since I plan on using a large amount of frag plugs in the future this could be an interesting DIY project. I am all about the DIY projects whenever I can. Read on to see my process and how they turned out!

Materials needed

The materials list for this project was pretty simple actually. I bought a 50 lb bag of play sand from Home Depot for $5 and a bag of Portland cement, 96 lbs of it, for $11. They sell concrete mixing tubs for about $6 if you need one but I had a bin at home to use. The only other thing we need is an existing frag plug to use a mold and a sharpie marker.

The process

First empty a large part of the play sand into the bucket or bin you will use to create your plugs in. Next add water and let it sit for a few minutes to really absorb through the sand. We want the sand to be wet enough that when we grab some and squeeze, it retains it’s shape when we let go. Think about the kind of sand to make a sandcastle with; that’s the consistency we want.

Now that we have our bucket of wet sand, it’s time to take the existing frag plug and press the top into the sand to create our disk. Hold the plug by the bottom as you do this, the part that goes into eggcrate, to help make pressing down and pulling it back out easier.

Pushing the disk part into the sand
Remove the plug for a disk mold

If you want a frag plug and not just a frag disk then we need to use our sharpie marker to push into the middle of the disk that we just made. How deep you go is up to you, it can always be trimmed back later if need be.
Note – I tried my first round to push the existing frag plug all the way into the sand but found that the bottom never turned out well. A sharpie was used my second attempt with MUCH better results.

Push the sharpie on the center of the disk mold

Now we have our mold all ready for us to pour in our mixture. So it’s time to mix the concrete and sand! Start with the concrete in a container, I used a disposable solo cup, and add a little water. Mix it up well before we start to add sand. I found it easier to add sand bit by bit as opposed to adding everything at once and mixing. Slowly add sand as you mix until we reach a ratio of 1:3 or 1:4. That is 1 parts concrete to 3 or 4 parts sand. Add water if you need to in order to keep the consistency a little bit runny. I like to think of thick pancake batter. It should run out thick but be thin enough to pour instead of drop out in globs. It may take you a few tries to find a good consistency; I took a few tries at least.

Our molds ready for the mixture to be poured

Next just pour the mixture over the molds we created. Be careful to not overfill the molds. Now we just wait. I have found about 12 hours works well.

Frags all poured (I had to make a few more to use all my mixture)

Carefully remove all the new frag plugs from the sand. I say to be careful because the bottoms can still break pretty easy at this point in time. If you don’t want to create a copious amount of plugs like I do you could leave them in the sand for a good 24 hours to really let them dry better. I chose to remove after 12 and put them in a bucket for air drying for a few days while I make more.

After a few days of air drying we can safely wash the sand off the plugs. I chose to use a 5 gallon bucket filled with about 1 gallon of tap water. Just swish the plugs in the water to remove excess sand and place in another dry bucket to continue our air cure. We’ll let them dry out fully for about a week before we start to water cure them. Here’s how my second batch turned out. My first batch, as expected, was terrible. That’s OK though I can still put them to use.

Water cure

The reason we cure them in water is because currently they will leech materials back into the water. This raises the PH of the water very high so to prevent any issues to our reef tank we need to cure them. If you only made a small amount of plugs you could put them in a mesh back and put the bag in the tank if your toilet. Every time someone flushes you are getting clean water over the frag plugs again. However I am making too many to fit in the toilet tank so I will use a 5 gallon bucket.

I still put my plugs into a mesh bag to make them easy to remove from the buckets to change water. I found this old laundry style mesh bag we had just laying around the house unused. I will be starting with using only tap water, more correctly my waste water from the RO water filter. This lets me put water that would otherwise go down the drain to good use. Simply cover the plugs with enough water and let them sit. I change the water out daily if I can remember as it’s only a gallon or two I am using.

We want to check the PH of the water periodically to make sure it goes down. My tap water tests at 7 which works well for this. Once we can get the water the plugs are soaking in to stay around a PH of 8 after a full couple of days soaking, we are good to go. I expect this process to take a few weeks but I will update this post to let you know how long it does take.

My next step is to try to make a silicon mold of the frag plugs so that I can have a more perfect frag plug. The sand seems to work but I would like a more consistent end product for my company. I’ll make another post if I can figure out how to make a silicon mold.

That’s it for making frag plugs. Pretty simple process although it takes a bit of time. This bag of sand and cement mix should let me make thousands of plugs at the very least so I consider the investment a good one. For people who only use a few plugs a month it might be worth it to just buy a bag on amazon. It’s really up to you to decide if the cost is worth it. I plan on eventually using hundreds of plugs a month so for me, it will pay for itself in no time.


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