I used the chambers at my house about 4 years ago. Have seen lots of the gravel base installations and personally installed one years ago. Here, use of the chambers requires 25% less length of leach bed. I needed that due to some topographical considerations. Also at that time, my son was an engineer for one of the manufacturers of those. Got employee price- saved a ton of money on the whole installation.

I priced them out a couple years ago for our build. Based on the prices I was given here in Michigan, I could not find any good reason to use them instead of gravel. Even with a reduced field size, conventional methods were cheaper.

There is a third option that is commonly being installed where space is at a premium or where the soil will not perk for a conventional leach bed.

They now make a three compartment septic tank that has aerators in the third compartment. The liquid discharge from this type of tank may be discharged directly into a storm drain or watershed.

We'll have a pump panel block system installed. It's a 50% reduction system.

Here in VA I was quoted the same price for both systems. The installer had had no problems with the infiltrators, but the engineers who did the perc test said they were starting to see problems with them. I opted for the infiltrators but then the Health Dept objected and would only issue a permit for the gravel. Who knows?

My leach bed area with the chambers does have different grass-growth patterns from the traditional gravel bed installations. Our County (NC) sanitarian says mine is normal and is working well.

We are building a house with 5 bedrooms (actually adding onto an existing house) and had to go from a 3 bedroom to 5 bedroom septic system - due to space limitations we had to go with the chamber system (Infiltrator is the only approved in VA) We had to hire a soils engineer who was a complete idiot and couldn't read the chart right - we ended up designing our system ourselves and having him stamp the plans (I am a Civil Engineer so at least knew a little bit about site drainage and issues) It reduced the size of our drain field in half over a conventional system. I would HIGHLY Recommend you double check your engineers calcs (if you can) no matter which system you use - just because they are a "Certified" soils engineer doesn't really mean anything in my book - Our "Certified Guy" had us putting in 2 more runs that we didn't need just because he didn't know how to read the chart right - and he had supposedly desinged 100's of these (feel sorry for the people who didn't check and probably installed more than they needed) We actually did the installation ourselves (VERY EASY all you do is dig a trench and snap the pieces together) - we installed the optional test ports (which my husband loves) you can open them up and stick a stick doen to see how much water is collected in the system and make sure they are working properly (when we took out our old system - 2 of the 6 lines were clogged and weren't even working and didn't look like they had worked in years. We have had ours in operation for 10 months now and all lines seem to be working great. I would HIGHLY recommend going with this system.

The vaults offer so much interface between waste water and soil that they seem practically bullet proof compared to the old perf pipe.

I wasn't offered much input, actually: my installer and the county sanitation engineer walked around my site and set the whole thing up between them. Made it easy to get the inspections, though...

With regard to which brands of the chambers are accepted within a particular jurisdiction, in NC each manufacturer must present his own case to the State Dept of Health. NC has accepted more than one manufacturer's product.