Although the original water heater was a 75 gallon gas water heater, the customer was running out of hot water with all of the demands of the household. A 100 gallon gas water heater was an option, but access prevented this installation. The other option was to install two 50 gallon gas water heaters that were plumbed in parallel.

Twin water heater installations can be plumbed in series or in parallel. A series installation has cold water going into one tank, being heated and then going into the second tank for storage. The second tank will fire to keep the hot water to the required temperature, but the first tank does the majority of the work over the life of this type of installation and hence will fail first.

A parallel system has hot water being drawn equally from both tanks at the same time if plumbed correctly. The advantage with this installation is maximizing the life of both water heaters.

Another advantage to a twin system installation is that if one water heater starts to leak, it can be isolated and drained down while the other is still operating.

With this installation, both water heaters were placed in drain pans with discharge lines going to the sump pit. This will prevent flooding the finished basement whenever the water heaters do fail and start to leak.