I will soon be expanding a cottage into a retirement home. I’ve put in a new septic system to service the larger house. The well water is great in this area of northern MI but is quite “hard”. I’d like to install a water softener but am told by some that the salty backwash from the softener regeneration can’t be discharged into the septic system. Will the salty water damage the concrete holding tank, kill the bacteria or is this OK?
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I don't think it's a good idea to discharge softener water into a septic system. We have always installed separate drains or drywells for that water.
Soaps and detergents are bad enough without adding salty water to the mix. There really isn't a whole lot of salt in the discharge, but why take a chance and why add more water to the system than you absolutely have to.
There have been two reasons proposed for not allowing water softener backwash into septic tanks: the effect of salt on microbes in the tank, and the effect of salt on clays in the soil. The most common thinking among researchers seems to be that if you want to dispose of the backwash into the drainfield, that's not a problem, but you should bypass the septic tank.
I don't think that the issue is settled. Experience seems to indicate that for most homes it's not a problem. On the other hand, why take a chance? As Bojangles suggests, a separate small drywell is a good alternative to putting it in the tank.
The back wash isn't sewage and could be discharged to the ground surface without creating a human health hazard, but plants wouldn't like it much.
FIL has been dicharging his backwash or regeneration rinse from his water softener into a plant bed for three + years now. The plant bed contains MIL flowers. So far we have seen no adverse affect on the plants.
Maybe it takes a lot more time to get a large enough salt build up in the soil to adversely effect the plants?
I googled the reaction chemistry of water softeners, but haven't found out how the regeneration discharge is handled.
There was a report by an Italian scientist recently of a test where salty water (sea water) was applied in some proportion (may 10%) to common vegetables like asparagus. It turned out that the salty water caused and INCREASE in the growth rate and production.
Might be worth searching for that report to show to our green thumbed wives.
That's interesting. Some water softeners use potassium chloride instead of sodium chloride. Potassium, of course, is an important ingredient in fertilizers, so it could improve plants. But I would have expected a softener using sodium chloride, which is more common, to have a negative effect over time. It would depend at least somewhat on soil chemistry and the plant species. It might also depend on whether or not the water softener is properly adjusted and operated.
Cargill Salt did a single study that indicated sodium chloride discharge isn't harmful, but that's the only study I know of that shows that. It may just be that the general assumptions made by many of us are wrong--won't be the first time. I'm going to have to try find out more.
Long term it may contaminate the soil in the flower bed, but I think it may be in the 10 to 20 year range, depending on water usage.
From what I can find with ion exchange softeners, the regeneration and rinse is just the opposite of the intial softening cycle. If that is the case then there would be a very small amount of sodium in the discharge. Most of it would be calcium and magnesium originaly removed durring the softening phase.
Hmm !
I wonder if our local water company would do an Na+ analysis on the discharge water. Maybe even one of those old boiler test kits I used would give me some idea.
Gotta be a simple test that support or disprove the high salt concerns about water softeners.
I believe it's the chloride more than the sodium that's harmful. And it's only harmful to most plants when it builds up to certain fairly high levels -- beyond the point where you see salt crusting on the ground. Finally, there's a lot of variability in salt tolerance between different plants.
What is wanted is not the will to believe, but the will to find out, which is the exact opposite. --Bertrand Russell
http://extension.missouri.edu/webster/ag-edge/waste-home/watersoft.html
I will recommend that you install a metered-head softener (as opposed to a cheapy day-clock model) and get a hardness test so that you can set the machine's regeneration properly. This will ensure that you always have soft water while using the minumum amount of salt required. Think $$$ saved on salt and less discharge volume to the tank and drainfield. Whenever I've swapped out an old day-clock model for a metered-head, the owners have always been amazed with how much less salt they use.
Edited 5/19/2008 11:46 pm ET by HootOwl
In our last house we put in a big water softener and a new septic tank.
For the discharge of the softener I ran it high through the basement wall above ground and turned it downward right outside into a bigger pvc pipe. The two pipes weren't connected so there was an air gap. I just ran the smaller one into the bigger one for about 6". So it shot down into the bigger tube.
From there I made sure the line had fall all the way to daylight out at the edge of the lawn. I didn't have to bury it very deep because it drained every time it was used.
The air gap let the drain line clear after every use.
It was pretty easy and I knew I wasn't overloading our septic system.
Over about three years I saw no change in the vegetation where it discharged. There was some deer activity though. We had lots of deer. Maybe they smelled the water or the salt. If there was enough salt buildup they would start eating I think. Just like a salt lick.
Are you located in a place that doesn't freeze?
I'd like to try something like you did, but I am concerned that the Minnesota winter would freeze my pipes.
Yes I am (or was) in a place that freezes. I'm not sure how much experience you have. I thought I explained it pretty well.
"From there I made sure the line had fall all the way to daylight out at the edge of the lawn. I didn't have to bury it very deep because it drained every time it was used."
The pipe drained every time it was used.
"The air gap let the drain line clear after every use."
Do you know what an air gap is?
Do you know what fall or pitch is?
I can explain but you need to ask specific question so I can answer them. I'm not trying to be hard about this. I just don't know what you know. You know? ; ^ )
I am concerned that when the softener runs at 2:00 AM, and it's -25 F outside, the water will freeze in the pipe before it can drain.
The tubing coming out of the softener is pretty small diameter. How much larger should the drain pipe be that the tubing drains into?
How much pitch do I want?
You can always arrange it with an air gap that will overflow in a "safe" fashion. Worst case add an upward-facing tee inside the house that runs to a drain.
What is wanted is not the will to believe, but the will to find out, which is the exact opposite. --Bertrand Russell
I don't think it fill freeze that fast. It is salty so that makes it harder to freeze. When the softener cycles it comes out of the pipe pretty fast so I don't think it will have time to freeze. As it goes through the pipe it will warm the pipe up a bit so when it stops and drains it won't freeze immediately. It should have time to drain.
If the outside dia of the tubing is say 1" then you want the inside dia of the other tubing to around an 1 1/4" so there is room for the air to replace the water as it drains out of the tube.
My lawn had pretty good pitch so it drained well. Our house sat high because we were near a creek. I don't think you need much pitch because the water will be moving well when it shuts off.
If you are concerned about freezing then go out of your basement wall into soil below the freezing temps and dig a big enough hole to accommodate the water plus the gravel and then some. The whole thing will be under the freezing temps.
If you do it the way I did it and it doesn't work what are you out? Some PVC?
I did the whole thing by the seat of my pants. It worked. Call me lazy but I didn't want to did a big hole.
If it's beyond your skill level or your seat of the pants level maybe you need to call a plumber?
It sounds like you are reluctant to do this. So don't. You can always run it into the septic system.
"...am told by some that the salty backwash from the softener regeneration can't be discharged into the septic system. Will the salty water damage the concrete holding tank, kill the bacteria or is this OK?"
For what it is worth, the local health department here says that in Indiana the softener MUST discharge INTO the septic system.
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Homeowners receive two distinct advantages from the best water softener for septic systems. It safeguards the home's plumbing system and water appliances first. Second, the best water softener enhances the biological function of the septic system without running the risk of tank flow problems.
https://www.usawaterquality.org/water-softener-for-septic-systems/
The link you posted does not seem to address the effluent from the regeneration cycle as it seems to focus on the residual salt in the potable water side of things.