Loss of Pressure - Water heater turns off 2

If they have poor pressure, going to a skinnier pipe would seem to be contraindicated, since the pressure drop in a skinny pipe would be worse than in a fatter pipe.

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>the water heater stops working

That means? Water stops flowing through the water heater? The flow coming out of the water heater is a lower flow? The flow coming out of the water heater is cold water, not hot water? Or something else?

>adjust the pressure switch in the heater, but he said he already had the technician look at it.

And the technician's report? Is there an internal pressure switch that might close a valve in the water heater? (I'd think it would just disable the heater, but what do I know?)

Increasing the size to 1" from 1/2" will help enormously and reduce pressure drop by a factor of about 15.

A 200m length if that size of pipe and hose won't let much water through.

Initially though just check for connections which reduce flow, any places where the hose or pipe have been crushed, naybe replace the hose with pipe.

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Danw2 said:

>the water heater stops working

That means? Water stops flowing through the water heater? The flow coming out of the water heater is a lower flow? The flow coming out of the water heater is cold water, not hot water? Or something else?

>adjust the pressure switch in the heater, but he said he already had the technician look at it.

And the technician's report? Is there an internal pressure switch that might close a valve in the water heater? (I'd think it would just disable the heater, but what do I know?)

Click to expand...

All great questions. I should have been more thorough.

The water heater turns off (turns off the gas to the heater) as soon as the cold water to the shower is turned on. So, while there is still water flowing through the heater, the heater's flame turns off....I'm assuming there is a pressure switch in the heater that switches off the gas when the cold water is turned on.

The technician for the water heater said it was the loss of pressure as well.

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I think what is happening based on how you describe the system is this.

There is a single cold water line to this person's house. There is a branch take off from this cold water supply line to an instantaneous water heater to provide hot water to the entire house or maybe just the shower? In any case when the cold water is turned on the water flows the path of least resistance which is mostly to the cold water outlet. There is too much pressure drop through the instantaneous water heater at any appreciable flow rate. In other words, the pressure at the connection point of the cold to hot water take off point is reduced so there is no more pressure to push the water through the hot water path at any significant flow rate.

In order to correct this you need to provide a way to maintain the pressure at the takeoff of the cold to hot water. This can be done by installation of a water back pressure regulator valve that can maintain the back pressure at the connection point to about 30 psi and have a maximum pressure drop of a about 5 psi at 2 to 3 gpm flowrate so as to keep available pressure at the cold water side. Or you can install an accessible manual gate valve on the cold water branch that you can manually partially close enough to keeP hot water flowing when cold water shower valve is open. See Sketch below. In escence what this does is provide about same pressure drop in both the hot water and cold water paths by inducing a pressure drop in the cold water path.

Here is link to Watts backpressure regulator. I could not find the flow verus pressure drop curves for this 1/2" size valve but I think it may have suitable capacity for a few GPM flow.

Snickster said:

I think what is happening based on how you describe the system is this.

Click to expand...

Yes, that's it!

And now that I see the drawing, I did a similar fix ~10 yrs ago here for someone else in a different location. But, I put in a homemade orifice in the cold water line... completely forgot about it.

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Exactly a restriction orifice would do too.

Without pressure and flow data you don't know if this is the issue or is it the 200m of rather small supply line.

Showers like about 15l/min or about 4 GPM.

A back pressure regulator may not help.

A trial whereby the hot water runs, but is too hot and then very slowly increase cold water flow until either the pressure drops and the heater kicks out or you get acceptable temperature. This is the manual version of what snickster has drawn. If it works then add in the valve to avoid someone turning on the cold tap too much.

That will tell you a lot.

If you can measure pressure the better.

The other option of course is that the user has a cold water tank he fills up slowly and then attaches a booster pump to it to flow water through the heater and shower faster than the supply can deliver it. Of course they can only shower for as long as there is water in the tank, but probably a lot cheaper than 200m of 1" pipe

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Any other cold water faucet in the bathroom would also work - the bathroom sink where it is easy to see the amount of flow that is related to any pressure drop.

I agree on the tank and the booster pump if low pressure is the cause.

Conceivably one could put the tank on a tower that is filled by gravity and passively provides less consistent pressure; it will be automatically limited by the available pressure when there is no flow.

A lower flow shower head is needed, although LittleInch's suggestion could also work. Basically, The problem is that at the flow rate that the shower is running is too high to maintain the supply pressure required by the heater. The solution is to increase the supply line size or throttle both the hot and cold water valves in the shower (much cheaper). A low flow shower head does the same thing. A pressure tank may help if some of the problem is due to the momentary pressure loss caused by having to accelerate the water in 200 meters of pipe when the cold water valve is opened.

LittleInch said:

The other option of course is that the user has a cold water tank he fills up slowly and then attaches a booster pump to it to flow water through the heater and shower faster than the supply can deliver it. Of course they can only shower for as long as there is water in the tank, but probably a lot cheaper than 200m of 1" pipe

Click to expand...

Thanks for the response.

Several of the users of the Aqueduct have 500 l-1000 l tanks on towers outside their homes. Not so much for pressure, but because we often loose our water source due to landslides, etc..., so this gives them a buffer.

One very wealthy family does have a tank and booster pump that they installed...but they have a large home with 5 bathrooms...it's definitely not the norm here. All other home that I can think of in our system only have 1 shower. Some homes still have dirt floors.

The question for the board of the aqueduct is who is responsible for such installations? It's the Aqueduct's responsibility for the network, but it would be the owner's responsibility for the booster pump. If the aqueduct purchases the pump system, other users will want the same.

I wish I had more details, and I'm working with the board to improve the system. They had no documents on the layout of their networks nor size of tanks. When I joined the board, they said they had 151 users (homes or dwelling) and I found they have 189...the additional homes were connected fraudulently. During dry periods, we've run out of water completely.

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Your other option is to twin the line with the same size pipe or hose starting from the house backwards. You might only need 50 m of twin pipe to get enough pressure at the shower flow rate.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Backpressure regulator may cut the cold water supply flow, probably during mid-shower. A sudden blast of only hot water would be dangerous. I doubt it would be allowed, but I have never read a plumbing code. I'd think you must have the same pressure in both hot and cold lines at all times.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Thank you for everyone's ideas and suggestions.

We ended up installing 200 meters of 1" pipe from the main header and that solved the problem. Cost for a trench (labor) and piping was under $1000US, and it helped a few other customers along the 200 meters.

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Thanks for letting us know the outcome. Too many posters never let us know, but glad we could all help you see what the irons were.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.