Caryl Owen, a loyal viewer of our TV show, is interested in installing a tankless water heater in her home. Her plumber advised her that a tankless water heater would not provide sufficient water pressure for a multi-head shower system. Caryl emailed asking for our input on this issue. We checked with one of our experts, Justin Castleman of Castleman & Sons Plumbing. Here’s Justin’s take:
“Currently we have several hurdles to get over to properly install a tankless water heater:
1-Gas piping and meter- The tankless can’t make use of the existing gas line (a few exceptions) and in almost all cases the gas meter needs to be upsized to prevent starving the other appliances of fuel. This can cause sooting and premature failure of furnaces.
2-Hardness of water- You must have a water softener. If not the tankless will become clogged with mineral in short order and will need to be replaced.
3-Pressure loss- Most loose around 20 psi. If you have 60 psi coming into the home then we loose another 12 psi at the softener. Now we are down to 48 psi to the tankless and 28 psi out of the tankless. Take off another 5 psi to lift the water to the second floor (23 psi) and you will not have the performance you are looking for.
4-Efficiency- Most are mid-efficient appliances. If considering a model, it must be a condensing type or do not bother.
5-Incoming cold water temp- Most are rated for 7.5 gpm at a 35 degree rise. That’s ok in the south but in our region the water comes in the building at 40 degrees. The tankless is now throttling back to make set point and you are lucky if you get 4.0 gpm (3 faucets on at the same time at best.)
6-Cold water sandwich- This happens when you start running hot water and the tankless is sensing the ambient water temperature in the pipes (70 degrees) when the 40 degree water starts to enter the home the tankless has to recalculate the fire rate and a shot of cold water makes to the user (usually in the shower) but it does not happen all the time and is better with models having buffer tanks.
7-Flow rates- If you have a high efficiency lavatory faucet that only uses 1/2 pgm the flow rate is not high enough to activate the appliance and hot water never arrives.
8-Venting- Until the new high efficiency models came on the market that use pvc the vent kits were proprietary and very costly to install.
9- Water conservation- We now have the statistics to show that water use goes up in a building with a tankless. In part from habitual use (user uses endless water) and structural waste. Structural waste goes up because the appliance is located closer to the venting point and you have a greater volume of water in the piping system that must be evacuated at the fixture before hot water arrives. If wait times are already several minutes to the master shower you will likely see an increase in that wait time
10- Gas prices are falling- This means your savings in dollars will be much less and the appliance will likely never have an ROI (return on investment). Unless you have a large demand for hot water.
In short, a high efficiency tank type water heater can make use of existing infrastructure, costs less to install and is usually more efficient. They used to qualify for more incentives (rebates) but all incentives for domestic water heating ended the first of the year.”
Thanks for watching, Caryl and thanks for an interesting question. Thanks also to Justin for some great information. Check out Castleman Plumbing’s video web channel at http://www.castlemanplumbingtv.com/ or visit their website at http://www.castlemanplumbing.com/
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