Ok the problem still exists with tankless Takagi on demand water heater It runs and in the site glass Isee a blue flame . I called Tek customer service and was told to shut off the cold water supply to the heater then open the hot faucet if water comes out I have a cross connection and water did in fact come out and Steve on this web site a few days ago suggested that the cross connection may be at a single valve shower so I replaced the cartridges in the 2 showers Still not fixed. When I turn on the hot water faucet at the laundry room sink the water heater starts running but still does not fire off Now when I turn on the kitchen Kohler single handle faucet for hot it does not even attempt to start the water heater So I turned off the hot and cold water supplies to the single handle Kohler kitchen faucet to isolate it and still not fixed The control water heater temperature controller box says incoming 50 degrees out 59 and no flow The only recent change I did was to remove the garage sink and cap off the hot and cold with shark bite caps Who ever can figure outlaw to fix this mess is really good THANKS in advance Yours truly Need a shower THANKS



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do you have flushing/service valves at the bottom of the heater?



can you shut off the hot to the house, put a hose on the drain/flush connection and try to see if it fires?
you could also shut off the cold inlet and set up a washing machine hose to feed cold water in that way.

so, cold in the blue side and hot out the red side.
nothing in the house can affect the function of the unit.

Ok Packy would be more specific in detail
You said shut off hot to the house ? DiI do not have the flush fill stuff yet If I get this apparatus then I would shut off the blue lever hook up water from washing machine to the place with the threaded caps and feed the system leaving the red apparatus alone yes ? If I hooked up a garden hose directly to the cold water inlet would this do the same thing ?



Edited 2 times.

no, shut off the red ball valve (hot to house) leave blue open and hook hose to the red hose valve.
cold should flow into the heater and hot should come out the red hose valve.

option 2 would be to shut both red and blue ball valves. feed cold into the blue hose valve and have hose on red ball valve open for the hot water to come out.

what i'm trying here is to isolate the house piping to eliminate any possible cross connection.

simply feed cold via a hose and let hot flow out via a hose.

cabeesh?

try option one first as any water flowing thru the heater should fire it.

I will try it thank you Packy