Raising pressure with pump?

[Qwertyjjj]

We have the equivalent of city water at a cottage (it's actually a neighborhood pump and well supplying multiple houses).
A leak has developed in one of the underground lines and it's not fixable until spring (ground too frozen to dig up).
Water pressure has dropped to around 15-20 so is not really usable for showers.

I have a 20 gallon pressure tank and switch (40/60) that's unused in the winter. Wondering if I can connect a pump to it and install temporarily.
What I don't understand is how the pump can get city water into the tank if the flow rate and pressure in the line is so low. Won't the pump just suck in the initial water and then create a vacuum and suck air from the main line since as soon as it pumps, the flow in the pipe will be very low...

 

[LLigetfa]

If you connect a pump to mitigate the leak, there is a strong possibility that you will convert a pressure leak into a suction leak, possibly sucking in contaminated surface ground water!

I would suggest instead to setup a non-pressurized storage tank and fill it from the low pressure supply. You can then pump from that storage tank without sucking up contaminated ground water.

 

[Sponsor]

 

[Valveman]

Yeah something like this.

 

[LLigetfa]

Yeah something like this.

Except the float would connect to a simple fill valve, not a solenoid to control the well pump.
A reverse float switch could be placed at the bottom of the tank to shut off the pump on a low water situation instead of the Cycle Sensor.

 

[Valveman]

True. So the inlet to the storage tank would be more like this one with an electric solenoid valve or float valve.

 

[LLigetfa]

A reverse float switch could be placed at the bottom of the tank to shut off the pump on a low water situation instead of the Cycle Sensor.

To further clarify, "reverse" depends on your application. A regular sump pump float switch would be a "reverse" in this context.

 

[Qwertyjjj]

Since in this case, the jet pump on the house end would be pulling in water from an already pressurised system, how does it avoid creating a vacuum and just sucking in air occasionally especially if there's a leak further upstream?

 

[Bannerman]

the jet pump on the house end would be pulling in water from an already pressurised system

LL & Valveman both recommended using the 15-20 psi community water supply to fill a non-pressurized cistern, then use your pump, pressure tank and pressure switch to pump from the cistern to your home's plumbing system. This way, there would be no potential of a negative pressure situation created in the community distribution system which could draw-in contaminated water, silt etc into the distribution system.

 

[Qwertyjjj]

Yeah sorry, I just meant jets in general out of interest. Surely they always create negative pressure?

With the cistern, I assume the tank has to be sealed to avoid contamination as well?
How do I size the cistern? They only thing using a lot of water for a while is the shower

 

[LLigetfa]

I assume the tank has to be sealed to avoid contamination as well?

No, the tank would need to be vented. Of course consumption will vary but 100 gallons per day per person may be a good starting point. Do you happen to have a metered water softener? If so, it should give you consumption numbers.

 

[LLigetfa]

How do I size the cistern? They only thing using a lot of water for a while is the shower

The first thing you need to determine is how many GPM is available when there is no restriction on the flow. The second thing you need to determine is how many GPM you use. The storage only needs to supplement the difference.

I have a metered water softener which reports GPM and gallons used so for me it is easy. I use less than 5 Imperial gallons to shower. Of course that can vary as some showers can use more than 5 GPM and some folks like to take long showers.

 

[Reach4]

Commentary-- not a prescription:
Stuff can grow in cisterns. People don't often discuss that.

A low pressure cutoff could stop producing a vacuum, but it would be a pita or cause cycling potentially.

There really ought to be a way to throttle the pump more gradually as the incoming pressure drops below a threshold. A vacuum breaker would be easy, but would introduce air if too much water was being sucked.

 

[Valveman]

If there is a water leak in the incoming line now, it will become an air leak, letting air into the system if you try to draw directly with a jet pump. Going to the cistern means the incoming line will always be under pressure, not vacuum. It will still leak water, but your booster pump won't loose prime this way.

 

[Reach4]

If there is a water leak in the incoming line now, it will become an air leak, letting air into the system if you try to draw directly with a jet pump. Going to the cistern means the incoming line will always be under pressure, not vacuum. It will still leak water, but your booster pump won't loose prime this way.

True.

Alternative, avoiding cistern, would be to have a low pressure cutoff, and throttle the output of the booster to where the low pressure cutoff never trips.

 

[Valveman]

You could also put a low pressure cut off on the suction side of the jet pump. If it got close to zero pressure the switch would shut off the pump and prevent a vacuum and drawing in air. But both of those ways could be a nuisance compared to a cistern.

 

[Bannerman]

I think in this case, the use of a cistern will be a temporary situation only until the distribution system leak is repaired in the spring.

Because it is a community water supply feeding multiple homes, the water will most likely be chlorinated. With a chlorine residual, bacteria growth in the cistern is likely not a big concern, particularly in a temporary situation.

 

[Valveman]

Once they have a cistern and booster pump, they will be in charge of their own pressure (can have strong constant pressure) and have a day or three water in reserve. I don't think it will be temporary.

 

[LLigetfa]

I think in this case, the use of a cistern will be a temporary situation only until the distribution system leak is repaired in the spring.

If the communal supply pressure is marginal, the cistern could become a permanent way of getting more pressure and bursts of volume.

 

[Qwertyjjj]

I'm actually not sure there's chlorination since although it's community water, it comes from a well or a few combined together. Can't smell any chlorine anyway.
Even when we did have our own well, the water would stay in the issue tank for weeks without chlorination and no-one seemed to bother. Not saying it's necessarily safe but I guess the filtration from the well depth helped somewhat.

Next thought: I used the pressure tank for irrigation water in the summer, we're allowed to take river water here. What's the best way to sanitize the pressure tank. Turn it upside down and pour in sanitizing water? Trying to avoid bleach due to the rubber diaphragm

 

[Reach4]

Next thought: I used the pressure tank for irrigation water in the summer, we're allowed to take river water here. What's the best way to sanitize the pressure tank. Turn it upside down and pour in sanitizing water? Trying to avoid bleach due to the rubber diaphragm

Diaphragm tanks use butyl (less permeability of air) rubber or a mix of that and EPDM. Maybe some are pure EPDM.

See Bleach Solutions row on page "213"

IIR = Butyl Rubber
EPDM=EPDM.

Use chlorine bleach solution.
Or don't.