After turning down my LED's for the last month and a couple of irregular water changes algea is under control athough not completly gone. Although I ahve changed a few things and removed stuff I have come to the conclusion I am suffering because of poor water changes. Looking back I probably do 50 litres every ~6 weeks which 5~10% per month if Im lucky. I have been looking at
http://www.reefkeeping.com/issues/2005-10/rhf/ . Seems quite a few reefs suffer a 18-24 month upset.
So instead of simply doing manual water changes I've decided this may inspire me to setup an automatic water change. Parts are on order for this and plan to be able to do up to a regular 30% WC if required which is only about 5L per day for me. That way I can also get away with topping up with cold NSW, maybe split the 5L into 2 cycles per day in winter, although doubt it would cause too much temperature fluctuation.
I was considering a double headed diaphram pump however found a RC thread on using the Tunze osmolator for topup of NSW and another tunze osmolator pump $35.00 to be used as a drain pump in the sump. Having the same type pump drain and topup with similar length hoses should provide a reasonable balance between drain flow = fill flow. In this scheme you simply switch the output of your osmolator between two pumps during a WC, the normal connection being RO and when on a Water Change you switch its output with a simple relay to another pump located in a NSW reservior.
The tunze ATO pumps are a simple impeller so ahve to be careful with syphon and flooding my sump. I have limited capacity to hold NSW outside the house plus hieght (syphon restriction) will see me use a 77L rectangular tank as the NSW tank outside. This tank outside will be slightly lower than my sump so it can never create a syphon.
This is pretty simple (Although the proof is in the final testing I know)
Use two tunze 12VDC osmolator pumps, 1 in the NSW reservoir outside to pump into the return section of the sump and another in the skimmer section of the sump to pump to drain. By using a 12VDC relay contacts on the output of your osmolator the tunze ATO is able to either topoff with RO or NSW (depending on if the relay is on or not). If the relay is deenergised the ATO is connected to the RO pump as normal. The real change to the ATO functions
Parts
240VAC plug in timer –turn the system on/off for say 3~6 minutes at a time maybe twice per day
12VDC plug pack to power the drain pump and relay coil.
2 new Tunze pumps $35 each
1 relay $10.00
12VDC Timer so the drain pump switches off maybe 1 minute before the ATO goes back to dosing RO water.
http://www.ebay.com.au/itm/AC-DC-12..._Equipment&hash=item23256603be#ht_2143wt_1073
Operation
1. The 240VAC timer energises the 12VDC plug pack for say 5 minutes once or twice a day
2 a) 12VDC energises the relay contact and the Tunze osmolator pump output wires go from RO to NSW pump
b) 12VDC also starts the sump pump and water is drained from the sump –An electric timer is also started.
3. As the sump is draining the ATO will simply start to topoff as normal. Except it now using NSW
4. A separate timer is used to turn off the sump drain say at 4 minutes. That way if the ATO is NOT balanced with the drain (flow in /= flow out) it gives the ATO time to adjust the sump level back to normal.
I would think using both the same type of pumps for in / out and same tube length the balance between whats going in ver out would probably be OK for a short period say <5 minutes. I know they are not correct and the sump level may end up being lower than normal. That’s why I want to turn off the drain and leave the ATO for a few minutes just in case it has to catch up.
5. The 240VAC timer deenergises the plug pack, 12VDC is removed from the system and the relay contacts simply switch the ATO output back to the RO pump as normal.
Optional Float switch in the NSW reservoir to detect if in fact there is available water to put back in.
FAILSAFE Scenarios
If the sump pump does not work i.e. drains nothing in its time period, its OK as the ATO although switched across to the NSW pump will just sit there and never turn on as the level has not changed.
No NSW -this is a problem and suggest I would get a float switch eventually in the NSW reservoir. However worst case is you drain say 5~10 litres and the ATO has nothing to top up with. When the time period has elapsed the ATO would switch back across to the RO pump and topoff with RO. (I think this maybe floored a little as I am not sure how long the tunze energises its outputs for with the ATO. I think it can only turn the pump on for a max of 12 minutes). Thus I could set a cycle of say 5-6 minutes per water change just in case.
Simple and independent + uses the features of the $250.00 ATO I already own that controls sump level.