Re: How big a sump and automated water changes.

[Bill Wichers <billw at waveform_net>]

At 03:56 PM 5/22/2003 -0500, you wrote:
> Bill,
>
> Not having ever used a sump and being in a similar situation (about to
> do a large tank, maybe two), I am curious about your comment regarding
> sizing the sump for water changes so that the tank level does not
> change.  We are in the planning stage of a new house and I want to have
> a couple of tanks, at least one of them pretty large.  I know that it
> will take a lot of work to keep these up so I am trying to figure out
> ways to automate them as much as possible.  I had already figured I
> would use sumps for hiding stuff and to do the water changes in the
> sump, and get the plumber to run some water and drains to the tanks to
> facilitate water changes.  If I could come up with a pretty fool proof
> method, try to automate the water changes too.  The sump being sized to
> handle a water change without changing the tank water level sounds like
> a good idea.  I would assume that the sump somehow has to have the
> capacity for all that water and then some but assumptions have gotten me
> in to more trouble than I can remember.  Would you please explain how to
> do this or refer me to a good source for info on this?


What you need to do is size your sump so that it can hold your entire water 
change volume and enough extra so that the equipment in the sump can 
continue to operate, and then add on some safety margin in case your 
circulation pump stops running. For example, if you need 4" of water in the 
sump for your equipment to function, and that 4" of water is 20 gallons, 
and if you want to change 20% of a 125g tank that means you need to hold an 
additional 25 gallons of water. This results in the need for at least 45 
gallons of sump capacity, and more would be better so you'd have some extra 
room. You also need to allow enough extra capacity in the tank to hold the 
water that might siphon down from the main tank in a power failure. If that 
amount would be 15 gallons (this number is determined from the difference 
in water levels between the tank's normal operating level and the level at 
which the overflow stops draining water from the tank), then your sump 
needs to hold AT LEAST 60 gallons to be safe in my example. Since these 
numbers have been 100% made up by me just this very minute, they may or may 
not have any relation to reality. The principle is the same though, just 
follow the idea and plug in your own numbers.

I recommend plastic sumps so that you can make modifications easily. 1/4" 
acrylic is cheap and can handle a DIY sump with up to about 12" high walls 
(more around 16" if you don't normally fill it to the top). If you want to 
try making your own sump get a 4x8 foot sheet of 1/4" acrylic from a local 
plastics supply house and cut it such that you can form a tank that will 
fit your needs. You will also need acrylic cement (Methyl Ethyl Ketone, 
nasty stuff, don't breath it) to cement the joints. You can also get ready 
made polyethylene tubs, and the famous rubbermaid "tanks" that are marketed 
for use in agriculture. A lot of the stuff is available from 
http://www.usplastics.com, but you can probably find the larger tanks and 
barrels cheaper locally since shipping is a killer on these things.

The only automated setups I know of use a system that basically 
continuously siphons out a trickle of water, and also continuously makes it 
up with a float valve. I'm planning on building a system myself that will 
be a bit better -- it will make batches of change water  (as in mix the 
water with dechlor and fetilizer and then heat it to the same temperature 
as the tank) and "flush" the tank, and then replace the old with the new 
water that has already been mixed with fertilizers and such. My plan is to 
use a microcontroller to control the process. I'm an engineer so this stuff 
is fun for me :-) I also want a tank I can just watch and strive to 
automate as much as possible.

Have your plumber install a cup sink on a 1.5" or 2" drain line (with a 
trap of course) into your tank areas where you want to put your equipment. 
A cup sink is basically a very small bowl (usually about 6-8" diameter) 
that mounts on the pipe and is supported by the pipe. It will give you what 
amounts to a permanently installed funnel that will make it easy to drain 
tank stuff into the drain line. Have the plumber install 1/2" water lines 
to the same areas and use a toilet valve or other small stop valve on the 
end. You don't need a large water line to feed your tank stuff, and the 
smaller valves like toilet valves will let you use small and economical 
water lines that are easy to handle in confined spaces. Do keep in mind 
that most of the clear vinyl tubing we use for aquariums is NOT capable of 
safely handling water line pressure (usually around 50-60 PSI). If you want 
to run full line pressure to a float valve you need to use the braid 
reinforced tubing, or a different type of tubing such as nylon that can 
handle the higher pressures involved.

        -Bill


> Also I would appreciate any suggestions on how to automate this stuff if
> anyone has done this successfully.
>
> Thanks
> Charles

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