Shower pressure improvement

[A W Warn]

Originally Posted by DeltaRon

At a suggestion of a friend, when hooked up to water supply, I also ran the water pump and almost doubled my water pressure. Just wondering if others had tried this?

I think you are seeing increased flow, not necessarily increased pressure.

Many add on pressure regulators that people use to protect their water hose restrict flow, since the regulator's internal openings are smaller than the hose's diameter.

If this is the case, the pump provides additional flow at the same time the city water provides flow.

ps:
I recently change a pressure regulator in a friend's plumbing. The inlet screen was full of sand and rocks. It still regulated static pressure when all valves were closed, but flow was almost blocked, so it seemed there was no pressure when water was flowing.

[Al and Missy]

Good points, Alan. Pressure, flow and restriction are analogous to voltage, current and resistance in an electrical circuit. While the pressure may be high with no flow, it can drop with flow depending on restrictions.

Al

[A W Warn]

Originally Posted by rmkrum

Mine tends to stay on continuously when we take showers. Takes a lot of water flow to run the tankless water heater as well. We turn the hot on full blast then adjust cold for the right temperature. DW loves her hot showers and that’s why we went to a tankless hot water system. (Happy wife, happy life)

It cuts on and off a lot when we flush the toilet or wash hands. I’m going to dig into the dank, dark recess where the pump hides and try to install an accumulator tank to smooth it out.

My pump is not variable speed by any means. I.e., noisy when running...bangs and vibrates the plumbing a lot. Accumulator and flex tubing on input and output should help a lot.

Which brand of pump do you have? If it is a Shurflo there is an adjustment screw on the pump head that can change pressure and flow rate. This might be out of adjustment causing the fluctuations you are experiencing.

https://www.youtube.com/watch?v=o2z2Q4oF4Co

[smithcreek]

Originally Posted by A W Warn

I think you are seeing increased flow, not necessarily increased pressure.

That's what I was getting at with my question a couple posts ago. When the water is turned on in the shower the pressure drops to say 40 psi and the pump by itself or the city water with the regulator by itself can only keep up with enough flow to pressurize the system to 40 psi. With both going there may be enough flow to keep the pressure closer to 50 psi while the shower faucet is open.

[rmkrum]

The way to be sure about that would be to put a pressure gauge on the water system inside the trailer. Then note the pressure reading when no water is flowing. Turn on the shower, and see how much the pressure drops.

One possible issue I just remembered. Some inexpensive pressure regulators actually restrict flow quite a bit when regulating water that is flowing. I had one of those, and attempts to get high flow dropped pressure enough that the tankless water heater didn’t like it. The gauge will tell the tale...

I got a decent adjustable pressure regulator with a gauge on it to put on the campground spigot. Works a lot better at high flow rates.

[Silvertwinkie]

FWIW, I have an Aquajet, and I have an in-line filter that filters to 5 microns on the city water connection. I do still have ample pressure, however, if I turn the pump on, it will draw from the tank (if I have water in the tank) until the pressure in the internal supply line(s) reaches about 50psi, at which time the pump will turn off automagically due to the neat little pressure switch that came with the trailer.



I've done pressure tests before, static pressure is not the same as dynamic pressure when a faucet or valve is open. Pressures can tend to decrease once valves or faucets are opened and at times increase before tapering back to average when a valve or faucet it turned off. Of course here too there are many variables, in-line filter, supply line size, type of shower head, faucet, etc, etc, where everyone will have a different experience to draw from.


However, those are my observations on my unit and I'm sticking to 'em, FWIW.

[link2dks]

Originally Posted by Al and Missy

Which is what I said twice.
Al

Ooops Sorry, I had even reads your posts earlier.

Dave S

[Tireman9]

I think there are a couple of details. Almost all RVs have a "Check Valve" on the water inlet that feeds the pressurized side of your water system. This is to prevent water from going from the RV into the local water system when we run our onboard pump.


A "Pressure Regulator" is different. It is designed to protect the RV water system from over-pressure which can fail hose & fittings on some RVs. Many of these regulators are set to 40 to 50 psi max but some can be set to up to 160 psi. You should check your RV literature and see what the company says for max inlet pressure for your RV.



You may have either or both a check valve and regulator.


Just another detail for RV owners to know.

[Silver Goose]

This is something that has always puzzled me. I can always get more flow from the shower when connected to city water if I turn the pump on. I’m admittedly a bit of an OCD nut and have a pressure gauge on my hose on the trailer side of the sediment filter and another inside the trailer displaying the pressure under the sink. I don’t see an increase in the trailer pressure when turning the pump on unless the city water pressure is lower than the regulator which appears to be set for about 50 psi. Since I see an increase in the flow at the shower or sink faucet, I have to conclude this isn’t a pressure issue but a volume issue. It seems the the mechanical nature of the pressure regulator restricts water flow to a degree and the water pump makes up the difference without actually changing the pressure in the plumbing.

[rmkrum]

Some pressure regulators can control pressure well, but the internal parts and passages are small, and restrict flow quite a bit.

[Al and Missy]

I couldn't stand it so I drew up the circuit for an electrical analog, made some wild assumptions, and guess what - for the assumptions I made the flow actually increases when the water pump is turned on. I'm sure that the amount of the increase (roughly 10%) depends highly on the assumptions I made about restrictions, but the flow does increase.

I learned something today, which coincidentally is a counter-proof to my tag line. I reasoned myself out of a position I had not been reasoned into.

Thanks everyone!



Al

[mefly2]

Depleting water from the AS tank ...?

[Al and Missy]

Originally Posted by mefly2

Depleting water from the AS tank ...?

If you are asking me, yes. In the case I analyzed the flow from shore water alone was 0.83. When the pump was turned on that went to 0.23 but the pump supplied 0.67 for a total of 0.90, almost a 10% increase in flow. I'm sure the numbers are highly dependent on my restriction assumptions.

Al

[Mitchsnider]

So, I tried turning on the pump for about 5 seconds while connected to city water (at my house) with my fresh water tank filled at 100%. Only about 5 seconds mind you. And yes, the flow obviously increased significantly. Then a couple of hours later when my wife was dumping the grey tank she asked me where all the water was coming from pouring out of the side of the trailer? So now whenever connected to city water the fresh water tank is being filled. I tried completely draining the fresh water tank and then using the pump to get most of the rest out the faucets. Turned the city water back on and watch as the fresh water tank slowly fills over severals hours. Bad advice turning on that pump while connected to city water. It made a valve in the pump fail on my 4 month old Airstream.

[A W Warn]

Originally Posted by Mitchsnider

So, I tried turning on the pump for about 5 seconds while connected to city water (at my house) with my fresh water tank filled at 100%. Only about 5 seconds mind you. And yes, the flow obviously increased significantly. Then a couple of hours later when my wife was dumping the grey tank she asked me where all the water was coming from pouring out of the side of the trailer? So now whenever connected to city water the fresh water tank is being filled. I tried completely draining the fresh water tank and then using the pump to get most of the rest out the faucets. Turned the city water back on and watch as the fresh water tank slowly fills over severals hours. Bad advice turning on that pump while connected to city water. It made a valve in the pump fail on my 4 month old Airstream.

The use of the pump and city water at the same time did not cause the pump to fail. This practice is encouraged by Airstream, and it is written into the owners manual.

If your pump failed while you were doing this, it was coincidental, not the cause.

[A W Warn]

Originally Posted by rmkrum

<<snip>>

This “run the pump to boost city water pressure” is Airstream legend, not plumbing facts...

I used to think this same way, but wrongly. (because I did not consider and understand basic hydraulics)

I was confusing and using the words "higher pressure" to describe "higher flow".

Flow rate (GPM) is a measure of volume over a set time.
Pressure (PSI) is a measure of resistance to flow.

When a hydraulic system is connected to two supply sources (city water and pump) both can supply flow as long as an outlet valve is open (less resistance). Once the valve closes, then the supply with the higher pressure will overcome the lesser, as you described.

Higher flow rate coming out of a shower head seems like increased pressure, but that is not the case. There is just more water available.

[A W Warn]

This describes the difference between flow and pressure far better than I can.

https://youtu.be/X0vGnzk4r6E

[link2dks]

Someone following this thread needs to do a test. Put a 5 gallon bucket in the shower, put the shower head in the bucket. Then:

1. Fill the bucket to the top using only city water pressure and time it.
2. Fill the bucket with city water pressure and your pump on, time it.
3. Fill the bucket with your pump only, time it.

Tell us what you find out, should be interesting.

Dave S