# Pressure drop



## OldSchool (Jan 30, 2010)

Does anybody know the standard pressure drop across a tankless ...????


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## nhmaster3015 (Aug 5, 2008)

It depends on the tankless.


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## 504Plumber (Jan 26, 2011)

Drop after peak demand is met?


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## rjbphd (Feb 5, 2010)

OldSchool said:


> Does anybody know the standard pressure drop across a tankless ...????


 Isn't it printed in the manuel??


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## UN1TED-WE-PLUMB (Oct 3, 2012)

Too much. 

I've noticed it after opening more than 2 fixtures.


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## OldSchool (Jan 30, 2010)

It's a Bosch ..Pro series

I got 65 psi static pressure on cold ...with tub running it drops to 55

On the hot side 65 static and 40 when it's running

So I am getting 15 psi drop across the heater


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## UN1TED-WE-PLUMB (Oct 3, 2012)

Sounds normal.


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## gassyplumber (May 1, 2011)

Doesn't the Bosch unit control the flow through the unit to maintain desired set point. Too much flow and the flow control chokes down.


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## johnlewismcleod (Apr 6, 2012)

Some tub valves dump between 10 - 12 gpm. Even if the tankless isn't throttling to maintain set point, at that volume/velocity of water moving through the heat exchanger the friction loss will be significant.

Just give the idiot his money back and be done with him :surrender:.

He's going to cost you more than you charged him anyway before he's done with you :thumbdown:


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## OldSchool (Jan 30, 2010)

So far it sounds like nobody has a clue ...

Tried tech support but 45 minutes on hold is just a little to long


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## UN1TED-WE-PLUMB (Oct 3, 2012)

Next you'll get a complaint about a cold water sandwich:yes:


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## UN1TED-WE-PLUMB (Oct 3, 2012)

They'll want you to calculate gpm. 

What type shower faucet is it? If its an old high flow faucet then the one fixture alone is maxing it out.


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## johnlewismcleod (Apr 6, 2012)




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## justme (Jul 4, 2012)

One option to correct the pressure drop would be to install a mixing valve after the heater. Increase the volume by raising the temperature at the heater and then mixing it to a desired temp.


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## OldSchool (Jan 30, 2010)

The customer is saying that the water temp fluctuates .. I was there no fluctuation .. Test pressures and this is why I am asking the question


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## justme (Jul 4, 2012)

a mixing valve would help with that problem also, and increase the effectiveness of the heater.


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## UN1TED-WE-PLUMB (Oct 3, 2012)

A co worker had the same problem with a Bosch tankless. He called the tech support line and they told him to install a 6 gallon electric buffer tank.


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## Plumberman911 (Dec 23, 2012)

All I can add is I've set three Bosch tankless. Have had similar problems and they wouldn't maintain temp it would go hot cool. One of them the gas regulator was malfunctioning. The other problem is Bosch just sucks. And customer service does too


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## ChrisConnor (Dec 31, 2009)

OldSchool said:


> The customer is saying that the water temp fluctuates .. I was there no fluctuation .. Test pressures and this is why I am asking the question



Fluctuates in all the fixtures or just the shower? Possibly a bad pressure balancing spool?


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## johnlewismcleod (Apr 6, 2012)

Plumberman911 said:


> All I can add is I've set three Bosch tankless. Have had similar problems and they wouldn't maintain temp it would go hot cool. One of them the gas regulator was malfunctioning. The other problem is Bosch just sucks. And customer service does too


There are many. many truckloads of crappy Bosch tankless out there, but the new generation is supposed to be much better than the old.

Keyword there, of course, is "supposed".


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## Gettinit (May 9, 2012)

If he can't show me, it is fine. It sounds like he is imagining it or he is trying to find a way to make it fail. An explanation of how the system works may be in order. If this is "that" guy and he wants it out that bad give him a figure to change it.


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## rjbphd (Feb 5, 2010)

Sell him a tan k water heater


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## UN1TED-WE-PLUMB (Oct 3, 2012)

A tankless heater delivers the water differently than a conventional tank type. 

The customer just has to get used to it. 

I always tell customers this when they ask about a tankless.


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## UN1TED-WE-PLUMB (Oct 3, 2012)

rjbphd said:


> Sell him a tan k water heater


Either the Vertex or the Effex. Both nice heaters, both high efficiency, the Effex you can do cheaper than a tankless. Vertex would be about the same.


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## rjbphd (Feb 5, 2010)

UN1TED-WE-PLUMB said:


> A tankless heater delivers the water differently than a conventional tank type.
> 
> The customer just has to get used to it.
> 
> I always tell customers this when they ask about a tankless.


Also, I tell them the payback is 12 to 15 years on the average conversion.


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## johnlewismcleod (Apr 6, 2012)

I can't say why, but for some reason I think I know this customer of yours.

I hope I'm wrong, but my feeling is that you'll never satisfy him no matter what you do. 

Good luck, brother.


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## JK949 (Mar 18, 2009)

Did you supply and/or install the unit?

My boss is done troubleshooting tankless units, especially if improperly installed and not maintained. Give an incentive for a proper install or leave them to deal with Bosch.


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## OldSchool (Jan 30, 2010)

JK949 said:


> Did you supply and/or install the unit?
> 
> My boss is done troubleshooting tankless units, especially if improperly installed and not maintained. Give an incentive for a proper install or leave them to deal with Bosch.


We installed tons ... I even have some out on rental .... Never had an issue ...

He says it is when they take a shower ... I know it's the shower faucet balancing cartridge sticking ... He argues it's not because he read it on the Internet ...

Try arguing with some one that doesn't want to listen ..

All I want to know with out waiting over an hour waiting for technical support ... What is the pressure drop across the tankless and then I wash my hands of him...


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## johnlewismcleod (Apr 6, 2012)

Ahhh...it's the shower, not the tub.

My apologies, OS...I thought you said it was the tub valve.

Pressure drop is variable depending on velocity (friction loss). So I doubt you will get a definitive answer from Bosch or anyone else, but at 1.5 gpm flow pressure loss would be negligible.


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## plumb1bob (Dec 14, 2012)

Bosch has different troubleshooting readings you can get from the control readout Not sure how to do it, can't remember, use nothing but RHEEM , there Cust. Service is fantastic, had a problem with tank they replaced it with new model


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## 504Plumber (Jan 26, 2011)

plumb1bob said:


> Bosch has different troubleshooting readings you can get from the control readout Not sure how to do it, can't remember, use nothing but RHEEM , there Cust. Service is fantastic, had a problem with tank they replaced it with new model


Rheems older 7.5 indoor are "defective" and I have gotten 2 replacements recently.


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## OldSchool (Jan 30, 2010)

504Plumber said:


> Rheems 7.5 indoor are "defective" and I have gotten 2 replacements recently.


C1050ES is the unit it pro series model


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