frankvw
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- Aug 8, 2009
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I'm at the south coast and we're lucky to have municipal water one day a week. But we have a lot of rain that is quite clean (compared to, say, the liquid industrial waste that falls in Gauteng) so harvesting rainwater is a no-brainer as far as I'm concerned. We already did that on a smaller scale (one tank) on our previous property and that worked fine, but I found that the biggest challenge was accurate chlorine dosaging. Rainwater is run-off from the roof, which means it picks up anything from bird dirt to monkey business, so it's not microbially safe unless you treat it. I've got leaf catchers, first flush diverters and inlet screens that stop 95+% of the solids, and I'm running the water out of the tank through a 5 micron polypropylene filters which leaves the water as clear as municipal water. (I've found that 1 micron filters clog up too quickly and are not really necessary in any case.) Which leaves antimicrobial treatment.
Previously I chlorinated all the water in the tank at once, first by adding Aquatabs (8.68 gram fizzy NaDCC tablets, two for a 5,000L tank), then with a pool floater filled with slow release sodium hypochlorite tablets. Both work, but the problem is that it's very hard to regulate the chlorine content in the water. The amount of water in the tank varies, and the amount of chlorine released from the pool floater is not constant. So 99% of the time there's either too much chlorine so that you've got swimming pool water coming out of your tap and the chlorine overwhelms the active carbon filter, or not enough so that the water smells musty due to decomposition of organic matter, which means that it's no longer microbially safe.
So I'm looking at in-line chlorination. And, since I'm doing this on a shoestring budget, ways to achieve that without breaking the bank.
We have four tanks: 3 x 5,000L that will store captured rainwater, and one 2,500L that is currently a municipal water backup tank. The idea is to pump water from the rainwater tanks through an inline chlorine dosage system into the 2,500 tank, so that the latter will act as a contact tank. Chlorine needs time to eliminate microbes, so you can't chlorinate water and then run it out of the tap immediately; it needs to sit for a certain amount of time before it can be used. So I'm thinking of running the water through the chlorinator into the holding tank in the middle of the night, using a simple timer to switch the transfer pump on and a float switch in the holding tank to switch if off when that tank is full.
Which leaves me with two challenges: finding an affordable inline chlorination unit, and an affordable pump with the right specs.
Starting with the chlorination unit: liquid dosing pumps are out. The few locally available pmodels are intended for much larger installations and well outside my budget, not to mention the challenges associated with liquid calcium hypochlorite or NaDCC (which is hazardous to store and handle). That leaves the simpler units using solid calcium hypochlorite tablets.
The main product on the SA is the Klorman in-line unit (e.g. here).
At R1,400 and up it's not cheap but it does seem to be the product of choice. However, there's an alternative for use with swimming pools, which is this one here:
This one is about half the price of the Klorman unit. But the specs are a bit sketchy, so I'm not sure what chlorine tablets or flow rates this one is made for.
So I'm open to suggestions here. Are there any other affordable options that work well?
Second, the pump. I need a fairly low flow rate. Standard clean water pumps for Jojo-type tanks are centrifugal pumps starting at 375W and a flow rate of 30L/min which is higher than I'm looking at. (Around half that would be ideal.) But smaller pumps for this application are hard to find; all I can see are pond fountain pumps (unsuitable) or even smaller aquarium pumps.
So I can use some advice here. All suggestions would be greatly appreciated!
// FvW
Previously I chlorinated all the water in the tank at once, first by adding Aquatabs (8.68 gram fizzy NaDCC tablets, two for a 5,000L tank), then with a pool floater filled with slow release sodium hypochlorite tablets. Both work, but the problem is that it's very hard to regulate the chlorine content in the water. The amount of water in the tank varies, and the amount of chlorine released from the pool floater is not constant. So 99% of the time there's either too much chlorine so that you've got swimming pool water coming out of your tap and the chlorine overwhelms the active carbon filter, or not enough so that the water smells musty due to decomposition of organic matter, which means that it's no longer microbially safe.
So I'm looking at in-line chlorination. And, since I'm doing this on a shoestring budget, ways to achieve that without breaking the bank.
We have four tanks: 3 x 5,000L that will store captured rainwater, and one 2,500L that is currently a municipal water backup tank. The idea is to pump water from the rainwater tanks through an inline chlorine dosage system into the 2,500 tank, so that the latter will act as a contact tank. Chlorine needs time to eliminate microbes, so you can't chlorinate water and then run it out of the tap immediately; it needs to sit for a certain amount of time before it can be used. So I'm thinking of running the water through the chlorinator into the holding tank in the middle of the night, using a simple timer to switch the transfer pump on and a float switch in the holding tank to switch if off when that tank is full.
Which leaves me with two challenges: finding an affordable inline chlorination unit, and an affordable pump with the right specs.
Starting with the chlorination unit: liquid dosing pumps are out. The few locally available pmodels are intended for much larger installations and well outside my budget, not to mention the challenges associated with liquid calcium hypochlorite or NaDCC (which is hazardous to store and handle). That leaves the simpler units using solid calcium hypochlorite tablets.
The main product on the SA is the Klorman in-line unit (e.g. here).
At R1,400 and up it's not cheap but it does seem to be the product of choice. However, there's an alternative for use with swimming pools, which is this one here:
This one is about half the price of the Klorman unit. But the specs are a bit sketchy, so I'm not sure what chlorine tablets or flow rates this one is made for.
So I'm open to suggestions here. Are there any other affordable options that work well?
Second, the pump. I need a fairly low flow rate. Standard clean water pumps for Jojo-type tanks are centrifugal pumps starting at 375W and a flow rate of 30L/min which is higher than I'm looking at. (Around half that would be ideal.) But smaller pumps for this application are hard to find; all I can see are pond fountain pumps (unsuitable) or even smaller aquarium pumps.
So I can use some advice here. All suggestions would be greatly appreciated!
// FvW
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