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Storage tanks - front detail

Project: A Water Storage Station

Past experience told me that, with a system as large as the one I was building, I would need a water storage solution that had enough capacity to provide both freshwater (RO/DI) and saltwater for at least a week in advance. Considering the approx. 550 total gallon size of the system, I figured I would need two containers with a minimum capacity of 65 gallons.

For saltwater, the 65 gallons would handle a 10% water change per week, with a little to spare. I estimated that the RO/DI requirement would run around 8 to 10 gallons a day (evaporation, etc.), but because the fresh water tank would be kept filled automatically using an automatic top off (ATO) device, I wasn't worried about the the 5 to 10 gallon deficit per week.

After browsing a number of prospective sites, I decided to go with 65 gallon Ace Roto-Mold tanks. They are very robust - indestructible, really.  The material they are made of (FDA approved polyethylene resins) is absolutely inert and the price, though not cheap, is very reasonable considering the quality of the product. Here is the spec sheet:

Water tank specifications

I was originally a little concerned about the comparatively small size of the tank's access opening - five inches. In the mean time, though, it's proved to be no problem at all.

Here is a pic of the tanks taken through the, not yet filled, hole in the wall for the display tank:

Water storage tanks

The first thing that had to be done before the tanks arrived was to build a stand for them. I had originally wanted to place the stands one above the other, in order to save floor space in the fish room. The more I thought about it, though, the more sense it made to place them side by side. That way I would have easy access to both tanks - and no standing on ladders would be needed.

I didn't want the tanks sitting directly on the floor so I built a stand out of 2"X4"s and 3/4" ply. I'm lucky in that I have both a jointer and a planer. That allows me to glue  2"X4"s together and then mill them into almost any dimension. That makes it nice for putting together very sturdy legs, etc. The pic is of the assembled stand, before painting and application of the top covering:

Water tank stand - finished

A few detail photos of the underside construction:

Water tank stand - details 1

The legs are all doubled up 2"X4"s. They've been notched out so that half the leg supports the frame and half supports the top. The way they are attached - epoxy glue and screws - makes for a very strong stand.

Water tank stand - details 2

Here you can see that I placed legs in the middle on the cross supports. I figured - can't hurt.

Water tank stand - details 3

When construction of the basic stand was finished, I first painted everything, but the top, with a good quality latex. I covered the top with Formica.

The tank on the left holds saltwater. The other holds RO/DI water. Here, you can see all the plumbing located on the front of the tanks.

Storage tanks - front detail

The pump is a Pan World 100PX. Seems to be a good pump, but it's quite a bit louder than I  expected. Although, because the fish room door is always closed, it isn't really a bother.

I've set up the plumbing so that, depending how the valves are set, the following can be accomplished:

  • transfer from freshwater tank to the saltwater tank

  • contents of the saltwater tank can be circulated - for mixing, etc.

  • both freshwater and saltwater can be emptied via the pump

  • both freshwater and saltwater can be emptied via gravity

In addition to the tank connections shown in the last pic, there is a 1/4" tubing line leading to the top edge of both tanks. These lines lead to the RO/DI unit and serve to fill the tanks with pure - zero TDS - fresh water. Each of the lines is terminated inside the tanks with a float valve. When the water level in the tanks reaches the float it rises, closing the valve. This causes the RO/DI unit to stop delivering water, thus preventing an overflow of the tanks.

The freshwater tank provides top-off water to the sump. This is regulated by the sump's automated top-off unit (ATO) and provides just enough water to replace the amount of saltwater that evaporates from the system. The fresh water is dosed to the sump using a 12 volt submersible pump, located at the bottom of the reservoir tank, via 1/4" tubing.

The saltwater tank provides water to the automated water change system, also using 1/4" tubing.

The only other connection to the tanks is on the freshwater reservoir. The connection carries the RO/DI automated top-off (ATO) float switch tree (note that a float switch is different than a float valve - the switch is electrical where the valve is mechanical).   This connection is located at the top of the freshwater tank, just to the side of the fill opening: 

ATO connection

As it's a little difficult (because of the relative small opening) to take pics of the inside of the storage tanks, here are some rough schematics:

ATO connection

Note that the 12V pump used to move the RO?DI water to the sump is the same pump that is used in Tunze's "Osmolator" ATO. It is very reliable, has a large head capacity, and is inexpensive.

The Float switch tree is constructed using 1/2" Sched.-40 PVC pipe.

ATO connection



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Abbi says...
Hi Tom, I have the same setup with my ato. My issue now is that there is a siphon forming after my ato kicks on! Have you had this same problem and if so what's a good fix? I ended up putting a T on the line in my water container but I'm still very concerned about this!
Great write up by the way!!
GlassReef: I integrated a 12V solenoid valve (about USD15.00 on ebay) with the 12V ATO pump. The valve is a normally closed model - the valve is closed if not receiving power. When the ATO pump starts the valve opens then closes again, as soon as the pumps is turned off by the ATO mechanism.
16th August 2015 10:03pm
brian decesare says...
One quick question ?Why is there a RO/DI float valve in the salt water res?I thought the salt reservoir was filled via the pump plumbed into the ro tank?If not what controls the ro water from diluting the salt water as the water changes are performed?
GlassReef: The saltwater tank is filled direct from the RO/DI. This is initiated by opening a valve from the RO/DI that sends the RO/DI water to the saltwater tank and diverts it temporarily from the fresh water tank. The float valve ensures that the RO/DI water does not overflow the tank.
16th November 2014 3:53pm
Bill Webb says...
Hey Tom,

Awesome write up, I definitely plan on stealing some of your ideas! I'm looking at some water storage tanks and was wondering if you had any issues adding the middle bulkhead to the curved surface of the tank?


3rd December 2012 2:54pm
Stu says...
Tom, do you need to clean the tanks every so often?
I find my salt tank to be an constant bother in this regard and wonder if it is normal or not.
The small openings in your tanks would be an issue for me to reach in. If you don't have any need to clean them would you have any speculation as to why that is?
GlassReef: Cleaning is occasionally needed for the saltwater tank - just as you mentioned. About every four months I drain the tank, unhook it from the system, and give it a good shot with a pressure washer. Not really much trouble. I could imagine that, with a preesure washer, there could some effort needed to get the tank clean because of the size of the opening.
23rd September 2012 1:32pm
Jon says...
Tom, your site inspires me more than any of the DIY or instructional sites on keeping reef tanks. You explain "why" and how not just how. I had a 60 gallon reef tank 5 years ago I struggled with. I just acquired for free a 180 gallon tank with stand for free and I can't wait to use your ideas with my own custom setup and get this tank rolling. If your site wasn't up I probably wouldn't be willing to attempt any of it. I just wanted to thank you for taking the time to inspire me in this hobby. I think the whole DIY part of it is a satisfying as keeping the fish and corals. So thank you, god bless and I would like to send you pics of my projects if you don't mind. I will be creating my sump in the next 30 days or so.
13th September 2012 8:27am

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