Drinking Water Storage Tank Inspection

Drinking Water Storage Tank Inspection

This customer contacted us for a drinking water tank inspection service.  The potable water for a commercial development is supplied by a private well. Well pumps filled two 15,000 gallon concrete water storage tanks that were connected in series. The tanks are piped together at the bottom which equalizes the water depth. The system was designed to supply 23,000 gallons per day however the development currently uses approximately 4,000-4,500 gallons per day. Due to the lower than expected consumption, the Massachusetts DEP required the tanks to be filled to 40 percent capacity, which allowed frequent turnover of water within the tanks.

This video shows the underwater rover scanning the tank bottom and sides.

The concrete water storage tanks were installed in 2012 and had not been inspected since the installation. There are canister filters and manganese/iron filtration at the pump station before the filtered water enters the tanks. There is a provision for future fire protection utilizing an 8’ ductile iron pipe which is presently capped. This modification would require a backflow preventer and MassDEP approval. 

A closeup of the damaged screen on the outlet of the overflow pipeA close-up of the screen at the overflow pipe outlet.

During the potable water tank inspection, CommTank technicians found 16 dead rats at the tank bottom. CommTank’s STI SP001 certified inspector examined the tank configuration and found mesh screen, installed over the overflow pipe outlet, had been compromised. The pipe had been installed at ground level and the rats were able to bend the screen top and enter the pipe. The angle of the screen also prevented these rats from exiting the pipe once they entered. It is believed the rodents jumped into the water to find another exit and died.  The customer was notified of the problem and they contacted the Massachusetts DEP for guidance on how to address the contamination within the tank.

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