Concrete Deterioration - Why?

[yspring]

Does anyone have any suggestions on why concrete risers, d-boxes and lids deteriorate. I'm guessing it's due to detergents, etc, but what are the ones homeowners should avoid? It's stuff like this that makes me love the plastic d-boxes, risers, etc.

Granted, homeowners should use as environmentally friendly products as possible, but in reality that group is a pretty small segment. I'd like to come up with a list of "bad" products and "good" products.

[etnpumper]

I think the hydrogen sulfide gas conbines with the moist atmosphere in the top of the tank and makes an acid that deterioates the concrete. The baffle below the water line always seems to be in better shape that what is above the water line. We have seen some baffles crumble in as few as 6 years. I wonder if it's a weak mix of concrete, household products, or is it the something to do with how well the system is vented?

Darryl

Goode Septic Service

[Aardvark]

I've found that most deterioration issues are associated with heavy garbage disposal usage, and when combined with bad ventilation is a disaster waiting to happen. The rotting food creates hydrogen sulfide. I've seen 1 year old septic tanks that are vented well (the neighbors can smell it) but were still deteriorating. We pump the tank, educate the homeowner about garbage disposals and a few other things and the foul smell and deterioration stop. I also seen 5+ year old septic tanks that weren't vented well and the 6" thick concrete lid fell apart after a couple typical sledge hammer raps. The under side of the lid and the concrete above the water line is a chalky green/white/yellowish crumbly mess. It's typical to be able to rub away 1" of concrete with the swipe of a glove.

I've yet to see a precast tank manufacture by one of the precast companies in our area cave in though. I have seen a few plastic tanks buckled (not from H2s though:)).

[mcminnspumping]

Hydrogen Sulphide gas is responsible for the concrete deterioation.
That is why the conrete below the "Water" line is still OK.
It is perfecltly normal for standard concrete to break down like this.
A lot depends on the quality of the concrete.
All septic tanks, Dizzy pits, risers, Etc, should be manufactured in SULPHATE RESISTANT CEMENT to counteract this deteioration, but this is not always done as this cement is much dearer than normal cement. Even the cement quantity in the concrete could effect it's usefull lifetime.
I hope this helps
Chers
John

[yspring]

Ok... now that we know it's hydrogen sulfide gas... is there any way to limit its production? Do detergents contribute to this? If so, which are the worst ones? Which are the "safest" ones?

[DaveW]

Crown Rot
I've heard it happens more in areas with high sulphur in the water.
I have not seen any studys or talk about household products contributing it would be interesting to find out if that is the case.
Lots of views both ways as to weather or not water softners contribute to it,I personally think they do.

[Stephen]

Use of a garbage disposal or any other means of getting excess food to the septic tank will raise the hydrogen sulfide levels, it also lowers the PH in the tank when the H2s and H2o mix.

I'm not sure about water softeners either, as far as concrete deterioration goes, but there is strong evidence that water softeners raise the salinity of the effluent causing the sludge in the tank to sit lighter and fluffier :) . This bring the sludge up into the agitation area of the tank sooner (maybe a year or two?). If I lived on a house with a septic system and a water softener, I would pump the tank more often to keep the sludge closer to the bottom.

[samiam]

believe it or not, the City of Seattle is moving towards Clay pipe, as the concrete system they have had since the 30's is deteriorating badly. Clay is inert and not subject to deterioration from effluents or gases.




Does anyone have any suggestions on why concrete risers, d-boxes and lids deteriorate. I'm guessing it's due to detergents, etc, but what are the ones homeowners should avoid? It's stuff like this that makes me love the plastic d-boxes, risers, etc.

Granted, homeowners should use as environmentally friendly products as possible, but in reality that group is a pretty small segment. I'd like to come up with a list of "bad" products and "good" products.

[Pete Morici]

believe it or not, the City of Seattle is moving towards Clay pipe, as the concrete system they have had since the 30's is deteriorating badly. Clay is inert and not subject to deterioration from effluents or gases.

Why not plastic????

[jhoffy4]

I've found that in our business, that an inexpensive vent installed in any tank will help abate the gas. It should be one with some sort of replaceable activated charcoal filter to control odors.

Jeff
Flemington Precast