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Low water pressure, booster or new tap?

We've lived in this area for 11 years, but in this particular house for just 15 months. Failure of the shower tiles and subsequent leaking into the subfloor of the master bath has led to other issues, one of which is low water pressure.

Pressure coming into the house, basement, is 46psi. Pressure on second story is about 34psi. Water district guarantees a min. of 40psi where it enters the home, so whatever resolution we take is our $$.

With the remodel of our master bath, we want to add body sprays along with shower heads and I'm reading that water pressure needs to be 55-60psi.

The first thing I did this past Saturday was to install a new PRV. The old PRV was fully maxed out and after consulting with the wat utility, we both hoped this was the answer. Unfortunately, no change in pressure which lead me to contact the water utility again and I found out the following:

The issue stems from 1984 when the house was built. There are 2 main lines and the builder chose to tap into the one on our side of the street which runs at 50psi. The main on the opposite side of the street runs at about 80-85psi.

Option 1 is to tap into the other main, pay new tap fees, permits for tearing up the asphalt road, etc., could run $2,500 or more.

Option 2 - As I understand it, add a booster pump and pressure tank.

Other items to consider:

Supply line coming into the house is 1" copper which feeds the water meter. Immediately after the water meter, line is reduced to 3/4" copper wich then gets reduced to 1/2" copper to feed the services (toilet, sink, DW, washer, showers).

Also, line comes in to home, water meter and PRV are behind a finished wall in one daughters closet. Easy access to piping, water heaters is on the opposite side of the house.

Stupid design.

Any other options, suggestions, insights is greatly appreciated.


You should be more concerned with gallons per minute vs the psi. You could have 100psi and you cannot deliver the gpm you need thru 1/2" pipe.

Your going to have to increase the size of the pipe from the main downstair directly to the shower minimal of 3/4".

There are booster systems that do not require the addition of an addition tank. Please see the link.


C of L Tech
Re: Gpm

He is right, I do a lot of this kind of trouble shooting. It is usually a flow issue, not pressure. Curious that you have a 1" meter reducing to 3/4". This is done to reduce flow and increse pressure, but would only work over a short distance. If mainline PSI is only 50, 40 PSI is reasonable. Unless your house is three or four stories tall, you shouldn't be losing that much PSI...HOWEVER, this is greatly dependant on the plumbing structure in your home. The standard trunk and branch set-up shouldn't be affected. Personally I would remove the PRV altogether. Most modern copper plumbing systems are rated to 120 PSI. If somebody gave you a quote of $2500 for a completely new tap, including fees, asphalt replacement, materials and permits, DO IT! In my municipality, a 1" tapping fee alone is in the $25,000 ballpark! Not to mention all the permitting and inspection fees. Here I would expect the whole job to be in the neighborhood of $50-60,000. On the other hand, if you install a booster pump, be sure to check if your area requires a backflow prevention device. Most likely it will, as per the Safe Drinking Water Act of 1975, any pump placed on a private potable water system must be backflow protected. In addition, you will most likely need both a pressure tank for the booster pump and an expansion tank for your water heater. Neither prospect is cheap, or easy. If it were, it probably would have already been done. At either rate, be careful. It is likely the house and appliances were built to a certain spec with the assumption of a max PSI of 50. As I said, MOST modern copper plumbing systems can handle 120 PSI, but, as I can't see it, I can't say for sure. Also, check all valves in the house, especially the main shut offs. If they are the old style gate valves, I would have them replaced wither newer ball style valves. In addition, check for any galvanized pipe or fittings, as these corrode over time and have a huge impact on flow dynamics in the pipe. look up pipe c-factor to see what I mean.

Re: Low water pressure, booster or new tap?

The builder made a mistake, for whatever reason, and now you're stuck with the result. To eliminate your problem, tap to the higher pressure supply line.

Re: Low water pressure, booster or new tap?

Pressure will be an issue if you are set on the fancy shower. For normal plumbing, the 46 - 50# pressure sounds adequate. Usually the problem that is described as a pressure problem is really a flow problem. If you use one fixture at your 46# it's probably fine. Multiple fixtures in use cause the problem. This can often be remedied with just a pressure tank, no pump. When the water is off, It fills. As you use water and the supply can not keep up the tank will supply what is needed. Then when you turn it off, it will refill again. If you really need higher pressure, you can put a pump before the tank. This will require a plumber, a cross connection control device and an annual inspection of the CCD by a plumber.

Why is there a PRV in place now? You don't need it and it is probably taking 5-7# off your system. Also if you have a softner or other treatment device, it too will take 5-7# off you system.

Some utilities will assist with the cost of a pump & pressure tank if your pressure is too low. 46# would be right in the ballpark for assistance. Check with your utility about that. The water people may not be aware of the program if there is one. Ask the building inspectors.

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