# Water heater pipe attenuation

Secan
There are 2 kinds of home instant bathroom water heater. The multipoint and single point (or shower heater). The latter is one where the unit is connected directly to the shower head. In the multipoint, its located a distant away and it serves multi points like sink and bath.

What would happen if i would use single point heater at bit distant away but serving the shower only? So imagine the single point heater has to pass thru the wall pipe (3 to 4 meters away) instead directly the less than 1 meter shower.

I don't want to use multipoint because existing wiring can only serve single point heaters and don't have space in the exact shower area.

How do you computate attenuation in water temperature as it pass thru the pipe?

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How do you computate attenuation in water temperature as it pass thru the pipe?
I believe that you will not notice any difference in temperature.
There will be certain time delay between opening of the valve and hot water flowing out, as the mass of cold water initially contained in the length of pipe between shower and heater flows out.

Secan
I believe that you will not notice any difference in temperature.
There will be certain time delay between opening of the valve and hot water flowing out, as the mass of cold water initially contained in the length of pipe between shower and heater flows out.

So the difference between Multipoint and Single point instant water heatera (tankless) is the Multipoint serve more than one output at same time and it is not the length to the shower head? You sure?

Gold Member
The latter is one where the unit is connected directly to the shower head
You sure it is connected to the shower head - err what do you mean by shower head - at the wall ( or just behind it ) or the sprinkler part - seems kind of wacky and dangerous electrically for the sprinkler part.

Multipoint serves several outlets, say a sink and the shower, tub; a single point serves just one outlet - maybe just the bath or just the sink, not both.

Lnewqban
Secan
You sure it is connected to the shower head - err what do you mean by shower head - at the wall ( or just behind it ) or the sprinkler part - seems kind of wacky and dangerous electrically for the sprinkler part.

Multipoint serves several outlets, say a sink and the shower, tub; a single point serves just one outlet - maybe just the bath or just the sink, not both.

The following is what i mean. All single points heaters i saw have the shower head connected to the unit itself. Of course it has a hose and not the sprinkler head coming from unit without hose.

256bits
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So the difference between Multipoint and Single point instant water heatera (tankless) is the Multipoint serve more than one output at same time and it is not the length to the shower head? You sure?
https://www.amici.com.ph/products/instant-water-heaters

256bits
Secan
https://www.amici.com.ph/products/instant-water-heaters

What i want to do is create an isolation point or water flow is controlled after the outlet of the single point. This is because i have an existing multipoint but it is defective and need high psi to activate. So i want to replace it with single point because i don't need multipoint.

What does it mean in the article the water is pressurised in multipoint because it is after the outlet? There is no pump inside a multipoint. This statement doesn't seem to make sense "Because the isolation points are located after the outlet of the multipoint heater, the water through the heater is pressurized."

Secan
What i want to do is create an isolation point or water flow is controlled after the outlet of the single point. This is because i have an existing multipoint but it is defective and need high psi to activate. So i want to replace it with single point because i don't need multipoint.

What does it mean in the article the water is pressurised in multipoint because it is after the outlet? There is no pump inside a multipoint. This statement doesn't seem to make sense "Because the isolation points are located after the outlet of the multipoint heater, the water through the heater is pressurized."

In other words. I want to replace this defective multipoint with a single point since it only serves the shower. Its a used house. Former owner used wires meant for single point so ill let my electrician connect the single point to it. But I am concern what would happen if the isolation point or part where water flow is controlled after the outlet valve of the single point (see prior message). Any ideas?

Gold Member
What does it mean in the article the water is pressurised in multipoint because it is after the outlet? There is no pump inside a multipoint. This statement doesn't seem to make sense "Because the isolation points are located after the outlet of the multipoint heater, the water through the heater is pressurized."
look at the picture you provided in post 5 and 8 ( the one just above ha ha ) .
Here is my take of the units.
Is the following what you yourself would consider to be the case for the units?
single point.
The valve is before the heater unit, so it goes city pressure --> valve --> heater unit --> shower head.

Multi point would goes city pressure --> heater unit --> your choice of valve( s) --> your choice of outlet ( sink or shower ). Heater unit is under city pressure.

But I am concern what would happen if the isolation point or part where water flow is controlled after the outlet valve of the single point (see prior message). Any ideas?
No clue. Your plumber people would know if a single point is made to withstand city pressure.
If I make a guess and I'm wrong and you have the unit burst with water everywhere, I would just not feel right about that, and might have to go join a commune.

Lnewqban
Homework Helper
Gold Member
What i want to do is create an isolation point or water flow is controlled after the outlet of the single point. This is because i have an existing multipoint but it is defective and need high psi to activate. So i want to replace it with single point because i don't need multipoint.

What does it mean in the article the water is pressurised in multipoint because it is after the outlet? There is no pump inside a multipoint. This statement doesn't seem to make sense "Because the isolation points are located after the outlet of the multipoint heater, the water through the heater is pressurized."

There are pressure sensors inside the multi-point heater that indicate the demand of water flow, so more heat automatically goes into the water in high demand conditions.

I believe that yours is a replacement in kind, as your old multipoint heater has always worked as a single point.
One of the pipes that are shown in your picture brings cold water into the heater, while hot water flows directly to the shower through the second pipe.

Most heaters have a built-in pressure relief valve, so any excessive pressure is automatically released to protect both the heater and the user from high pressure build up.
The outlet water temperature is controlled by a heat stabilizer in such a way that your shower gives steadily warm or hot water during pressure changes.

As previously advised, always check the installation instructions manual of your specific heater prior installation.

https://www.e-tankless.com/electric-tankless-how-it-works.php

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256bits
Secan
look at the picture you provided in post 5 and 8 ( the one just above ha ha ) .
Here is my take of the units.
Is the following what you yourself would consider to be the case for the units?
single point.
The valve is before the heater unit, so it goes city pressure --> valve --> heater unit --> shower head.

Multi point would goes city pressure --> heater unit --> your choice of valve( s) --> your choice of outlet ( sink or shower ). Heater unit is under city pressure.

No clue. Your plumber people would know if a single point is made to withstand city pressure.
If I make a guess and I'm wrong and you have the unit burst with water everywhere, I would just not feel right about that, and might have to go join a commune.

But if you turn the valve maximum in the single point. Is it not like multipoint as far as pressure is concerned? Btw my house water pressure is only weak at 20psi instead od usual 50 psi.

256bits
Gold Member
But if you turn the valve maximum in the single point. Is it not like multipoint as far as pressure is concerned? Btw my house water pressure is only weak at 20psi instead od usual 50 psi.
Yes . I know what you are getting at.
But, besides the unit itself and internal workings, the threaded connections have to withstand the pressure.
A connection to a shower hose is a lot different than a connection to the pressurized system.
If the shower hose connection leaks, it leaks into an already "wet" area with a drain.

Lnewqban
Secan
Yes . I know what you are getting at.
But, besides the unit itself and internal workings, the threaded connections have to withstand the pressure.
A connection to a shower hose is a lot different than a connection to the pressurized system.
If the shower hose connection leaks, it leaks into an already "wet" area with a drain.

Do single points have some kind of pressure limiter inside? Imagine connecting your single point right next to a water provider. If there is limiter inside i guess i can't replace my broken multipoint with single point because the pressure of the extended water outlet to shower would be much less?

Gold Member
Do single points have some kind of pressure limiter inside? Imagine connecting your single point right next to a water provider. If there is limiter inside i guess i can't replace my broken multipoint with single point because the pressure of the extended water outlet to shower would be much less?
Pressure limiter inside unit - that I do not know.

Honestly, I have an idea of how things should work, which is not the same as how they do actually work.
From my perspective, both single and multiple should have similar parts, just because, for several reasons. ( Say the outlet gets plugged for some reason building up pressure within ). But the actual designers may have decided that "oh they will never need that" and "that will never happen" due to the two different types of applications.

Do all singles hang in the shower stall, or are some made to be located outside the stall - would seem like a round about way for the plumbing connections, not to mention temperature control, yet that may answer your inquiries. Which would be post 10 by @Lnewqban for some tidbits on connections.

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Secan
I finally uderstood what caused the great pressure loss after water passed through the multipoint heater. Output is only 25% the strenght of input. It's the damned valves shown in red.

The holes are very small in the inlet. This is when valved turned on.

When valve turned off

This is the outlet with a big piece permanently blockage it.

I tried to google the name of the valve. What do you call it?

It blocked the pressure of the water causing some turbulence and heat and loss of pressure. No one caught it? The valve above should only be used for one faucet, so called angle valve. But I can't find the name of the mechanism inside it. Is yours like it too?

In a normal working multipoint heater. What percentage must be the output pressure. I couldn't find the answer with the google wildcard "water heater pressure loss".