Hot water storage tank

Mike Reavis_2

I came across a job where a plumber removed a copper boiler, and storage tank, and replaced the boiler with a tank heater, and kept the storage tank downstream from the new heater. I have my concerns about doing this. I would like to hear yours. The original boiler had a 275k input. The new 80 gallon hwh has a 200k input. The is no working recirc. What are your thoughts?

Mike

Rufus Laggren

Well...

Assuming you're talking about a DHW system, and the new heater was installed OK (air/gas supply, flu, piping, etc), that reduces possible problems to service life, and performance.

If the storage tank was 80g and the new tank-WH is 80g (and assuming the old setup was adequet) there is probably enough HW. Water temp might vary some, though I don't know it would change enough to be a problem. If there is no usage over a period of 8-10 hours or so (depending on actual heat loss from the storage tank) then HW temp might drop too low. However, 80g at 130 would stay toasty and useable for quite a while, even without any insulation. I suspect it probably works OK.

It would be nicer with a circ loop between the tanks, and it may not need a pump. If the storage tank is filled from the bottom (likely) that would need two small (1/2") lines teed to connect the tanks top-to-top and bottom-to-bottom. Shouldn't need a pump if the tanks are close, and 1/2" won't back-fill too much when the system is delivering water. If the storage tank is filled from the top (dip-tube), then only one added line connecting the bottoms of the tanks would be needed.

Service life might be 10 years or more. In SF I know of a 12 unit (12 bath) building running DHW off a 100g tank heater. Don't see how he gets away with it, but I get over there pretty often socially and it seems to have always worked (tenants haven't rebelled yet, and my shower always stays hot ); guy reports 8-15 years for a heater.

Rufus