Cost per gallon for water changes

[bg2311]

I've been working on an automatic water change configuration at home and it got me thinking: even with buying salt in bulk and mixing it with RODI water at home, as system volume increases or size/frequency of water changes increase the costs still add up.

I figure it's about 50cents/gallon for water changes on our 200gallon system. This is with Red Sea "blue bucket" in the 200gallon bulk bags. The advertised 200 gallons is when mixed to 1.021 and I'm not sure who would mix it like that. It's probably closer to 175 gallons per bag at $90/bag shipped. A 10% water change (20gal on our system) is about $10. I'm not taking into account power to heat and mix the water or RODI consumable filter wear and tear.

How much per gallon does it cost you to do a water change and how much do you change out each month?

 

[morganatlanta]

I change out 5 gallons per day on my 120 display. I recently switched to Live Aquaria Pro salt, which is $70 delivered for the 205 gallon box, so I should be getting around 41 days out of a box. I end up doing some water changes while cleaning and such, so I really probably get less than that, so I figure $60/mo. I also make a lot of water, so there are costs for filters and DI resin. I look at it as-- if water changes are preventing issues, that is where the savings are, but you can't know what you saved because the issues didn't happen!

 

[darrrenjmartin]

Cost depending on location…..Are you On Atlanta COA water? take your water bill then double it for sewer. One bill. Min avg $140 water/sewer.
The city assumes all water goes in the sewer including Ro waste. COA handnt managed the sewer infrastructure so there is now a water /giantsewer bill. There is an special agricultural meter installation which is does not have a sewer bill. Not cheap and still has the minumum monthly charge.

 

[rew1red]

I change 5 gallons (just shy of 10% of my water) once a week. I did some quick math for you, and estimate that I probably spend $1.50 on each change-- or $0.30 per gallon.

Item	Unit	Qty	Line	Notes
RO Water	$0.00984	15	$0.148	Permeate pump and a higher water pressure permits a theoretical 1:1 waste:water ratio. Assume a pessimistic scenario at 2:1 waste:water.
Red Sea Coral Pro	$0.00150	870	$1.305	55 Gallon Bucket at 48.5 lb. Mixed to 35ppt, a ratio of 38.2 gr/L. 22.7304 L (5 Gal) requires roughly 870 gr of salt mix.
Electricity, Mix	$0.10700	0.45	$0.048	I mix for three hours with a pump that consumes 0.8A. 150W for 3 hours, 450Wh, or 0.45kWh. My rate this time of year is 8.95 c/kWh, and in Summer 12.40 c/kWh. We'll average 10.70 c/kWh, pessimistically.
Electricity, Pump	$0.10700	0.0195	$0.002	Trivial, but I run a pump to transfer water to the tank. The pump consumes 80W, and we'll pessimistically say I use it for 15 minutes. 0.0195kWh
Total			$1.50