Can’t live in the home due to improper plumbing slowly killing the occupants. EXTREMELY weird problems at hand.

I’m a residential/commercial water-treatment project manager in northern Illinois trying to help with a very unusual case. This is far outside a normal water-softener/treatment appointment, and I’m not currently trying to sell the homeowner treatment equipment. I’m trying to determine what type of professionals/testing should come next and whether there is a plausible plumbing contamination pathway in which could cause the problems at hand.

Long story short, a water softener was drained to an ejector pit with no air gap, this ejector pit is also compromised allowing ground water intrusion, and the homes humidifier which is fed water from an infected water softener might be spreading deadly pathogens throughout the home. pets have nearly died, clients started experiencing bloody stool while living in the home, all of which has resolved since leaving to live with their parents.

The home is a single-family residence on municipal water.

The biggest thing I personally observed is this:

Chlorine residual is detectable from the exterior water supply, but I cannot detect any chlorine residual from the water once it enters the home.

This is with all existing water-treatment equipment bypassed. So the softener or other treatment equipment is not simply removing the chlorine during these tests.

That makes me concerned that something within the premise plumbing is creating a very high chlorine demand. Biological activity/biofilm is one possibility, but I understand chemical contamination, corrosion products, sediment, sulfides, iron, organic matter, etc. could also consume chlorine.

There is also a potentially significant plumbing defect.

The existing water softener was apparently installed with its drain line without a proper air gap, and the drain was submerged/terminated into a drainage system associated with a sewage ejector pit.

The ejector pit itself reportedly has an opening/failure at the bottom that allows groundwater to enter it. The homeowner reports that its behavior changes after significant rainfall.

The softener’s electronic control has now failed, but the questionable drain installation apparently existed for an extended period before that.

Previous testing of biofilm/material from the home reportedly identified:

• Roseomonas
• A non-enteric Gram-negative rod that could not be speciated

Pseudomonas aeruginosa has been suggested by others as a possibility for the unidentified Gram-negative organism, but as far as I know P. aeruginosa has not actually been confirmed, and I am trying to obtain the complete original laboratory reports and sampling methodology.

There are also unusual deposits/slime in portions of the drainage/sewer system that have been described as possibly iron ochre and/or sulfur-related biological material.

Client and I have also found bacteria colonies that have a bioluminescent biofilm that glows under UV around most drains and taps in the home, around the air ducts, AND most interestingly has been found in the homeowners ear wax too. client feels the bacteria spread is due to the softener providing bacteria laden water to their furnaces humidifier.

There are many other reported problems in the house, some of which may or may not be related:

The occupants report unusual odors, intermittent elevated VOC readings, combustible/methane-type detectors activating, severe corrosion of some electronics in the basement, possible sewer-air intrusion, groundwater problems, and significant health symptoms involving both people and pets.

A Certified Industrial Hygienist and other professionals are already investigating portions of the situation.

I want to be very careful here: I am not assuming all of those observations have one cause. I’m also not asking Reddit to diagnose anyone’s health symptoms or identify unknown chemicals based on smell.

What I’m primarily trying to understand is the plumbing/water side.

My questions:

1. Could a softener drain submerged into an ejector/sewer system without a proper air gap create a realistic back-siphonage or backpressure pathway capable of contaminating the potable side of the system of this nature?
2. What exact conditions would have to occur for contaminated water from that drain/ejector environment to migrate backward through the softener or into household plumbing?
3. Does the fact that municipal chlorine is measurable outside the home but disappears throughout the interior plumbing even with all treatment bypassed significantly change how you would investigate this?
4. What would cause enough chlorine demand within one home’s plumbing to reduce a normal municipal residual to essentially zero?
5. Would you suspect widespread premise-plumbing biofilm, chemical contamination, a cross-connection, stagnant/dead-leg plumbing, corrosion/sediment, or something else first?
6. How would you determine exactly where the chlorine is disappearing? My thought is to sample sequentially: municipal/exterior point → first accessible interior piping → progressively farther cold-water fixtures → hot water separately.
7. Would you collect matched microbiological samples at those same locations?
8. Would you leave the plumbing undisturbed initially so the existing condition can be documented, or immediately disconnect/remove the old softener and correct the improper drain?
9. Should the entire home be inspected for additional cross-connections/backflow hazards rather than assuming the softener is the only possible pathway?
10. What type of professional would you involve at this stage — licensed plumber specializing in cross-connections/backflow, municipal cross-connection inspector, environmental engineer, plumbing engineer, industrial hygienist, environmental microbiologist, or some combination?

My current thinking is that we need to establish a hydraulic and microbiological map of the house before recommending treatment.

For example, if chlorine is present immediately before entering the building but disappears at the first interior sampling location, I want to determine what exists hydraulically between those two points.

I would also keep potable-water samples completely separate from samples of ejector-pit water, drain slime, condensate, etc., and only attempt to correlate them if laboratory results actually support that connection.

Ultimately, I’m trying to answer two questions:

Where is the municipal chlorine being consumed?

and

Is there an actual pathway connecting the contaminated drainage/ejector environment with the potable plumbing that might cause the problems at hand?

Any plumbers with experience in cross-connections, backflow, ejector systems, contaminated premise plumbing, or unusual chlorine-demand problems would be greatly appreciated.