City Water Pressure Booster

[JRH]

I have city water but the pressure is lousy. Static pressure is around 45 but when you cut on a faucet the pressure drops to a low figure. Water enters my house at between 45 and 50 psi with a flow of 17 gpm but flow is reduced to 6 gpm at most of the faucets in the house. I have 3/4 inch pex on all the main lines with 1/2 inch branch lines. How low the pressure goes I am not sure but 2 people cannot shower at the same time. My question is does anyone have any experience with the residential water pressure booster pumps? Do they work and do you need the tank with them? I see some that just have a pump. Any reply appreciated.
Thanks
JRH

[HayZee518]

are there any complaints from other folks? my house pressure is around 80 psi. you can use a booster pump to a storage tank otherwise you'll get on off pulsations from the pump cycling on - off.

[LazyPup]

A boost pump will not resolve your problem.

Under the IRC (International Residential Code) a boost pump & pressure tank is to be installed only when the municipal supply “Static Head Pressure” to the structure is less than 40psi. Ref:IRC-2903.3

Under the UPC (Uniform Plumbing Code) a boost pump & pressure tank is only to be installed when the municipal supply static head pressure is less than 15psi - ref: UPC-608.1 (20psi when the shower has a pressure balance control.)

A pressure-reducing valve is required whenever the static head pressure exceeds or is likely to exceed 80psi.

You post states that water enters your house at 45 to 50psi but that is not true. The static head pressure is 45 to 50psi however it must be noted that “Static Head pressure” only exists when there is no flow, hence the term “Static”. The moment that flow begins the static head pressure immediately drops to “Dynamic Head Pressure”; or what is commonly referred to as “Working Pressure”.

“Dynamic Head Pressure” is Static head pressure less “Friction Head Loss” and “Vertical Static Head Loss”.

“Vertical Static Head loss” is the opposition to flow in a vertical riser caused by the physical weight of the water in a vertical column and VSHL can be computed as 0.434psi/ft of vertical rise from the physical source of pressure or the “Prime Mover” to the physical elevation of the outlet. (In the case of a municipal water supply the prime mover is the municipal water main).

Example. Let us assume the municipal water main to be 10’ below grade and you have a bathroom faucet on the second floor, which is 15’ above grade. The vertical differential from the prime mover to the faucet would then be 25’ therefore the Vertical Static Head Loss would be 0.434psi/ft x 25’ = 10.85psi loss.

While we were able to use a constant to compute “Vertical Static Head Loss”, computing “Friction Head Loss” is not so easy. Friction head loss is the physical loss of pressure, which results from friction between the flowing liquid and the interior pipe wall. Obviously there is no friction when the liquid is standing still but the moment that any faucet or other outlet is opened and flow begins, the liquid passing through the pipe exhibits friction loss from rubbing the interior of the pipe, and the faster the rate of flow (velocity of flow) the greater the Friction Head Loss. In addition to the problems associated with pressure drop in the system we must also consider pipe wall erosion. In copper pipe, pipe wall erosion will occur when the velocity of flow exceeds 10ft/sec and in plastic pipes erosion occurs when the velocity exceeds 15ft/sec, therefore the codes require that we must compute the volume of flow and select a pipe large enough to keep the velocity of flow under 10ft/sec in copper pipe or 12ft/sec in plastic pipe.

To determine the proper pipe size we must first make a list of all fixtures connected to a line, then we refer to the code tables to determine the required volume of flow for each fixture. From this we can then compute the total volume of flow required for a worst-case scenario where all faucets and fixtures on that line are open at the same time. Once we know the total volume of flow required to meet the needs on any line, we then consult the published “Friction Head Loss Tables” for the type of pipe we intend to use.

By example, let us consider a simple house with one bathroom group, (Lavatory, Bathtub/shower & Tank Type Watercloset), a kitchen with a sink & Dishwasher, a laundry with just a washing machine hookup and one outside hose bib.

Under the IRC we would then consult table: IRC-T2903.1 to find the minimum fixture requirements:

FIXTURE GPM Flow PSI
Lavatory………………..2 …………………………….8
Bathtub/shower……….4…………………………...…8
Watercloset……………3 ……………………………..8

Kitchen sink…………...2.5 …………………………...8
Dishwasher …………..2.75 …………………………..8

Washing Machine ……4 ………………………………8

Hose Bib ………………5………………………………8
TOTAL 23.25gpm

Let us now assume that we are installing Polyethylene SDR9 pipe for the house main water line (line from the municipal main to the structure main water shutoff).

Consulting the PE pipe Friction loss table we find that with a flow rate of 23gpm we could use the code minimum line size of ¾” pipe however if we do so, the Friction Head Loss for the house main water line would be 41.32psi/100ft. (0.413psi/ft).

Let us now assume that our house is 50ft from the municipal water main. If we were to open all the valves in the house simultaneously the Friction Head Loss in the house main water line from the municipal main to the structure would then be 50’ x 0.413psi/ft = 20.65psi. This means that if we had the afore mentioned 50psi static head, when all the valves are open the resultant Dynamic Head at the Main Water Shutoff valve in your house would drop to 50psi – 20.65psi = 29.35psi.

If we were to then deduct the vertical static head to the lavatory in the upstairs bathroom (computed above) we would have a net pressure of 29.35psi – 10.85psi vertical static head = 18.35psi at the lavatory faucet but then we would need to go back and compute the friction head loss for the pipe from the Main water shutoff valve in the basement up to the lavatory on the second floor and once we factor that in it is very likely that we could not maintain the code required 8psi minimum at the faucet.

Now I would wholeheartedly agree that it is very unlikely that you would ever have all the faucets and valves in the house turned on at the same time, but none-the-less, for design purposes we must engineer for the worst-case scenario.

For the example at hand the simple solution would be to increase the size of the house main water line from the code minimum of ¾” to 1”. By doing so we would reduce the Friction head Loss in the house main from 20.65psi to 6.38psi loss. When we consider that the cost of installing the main water line is primarily labor with only a mere fractional cost of upgrading from ¾” to 1” pipe, it then goes without saying that we should select the 1” pipe.

One of the most common problems we see in the plumbing trade is when homeowners buy an older home that no doubt has the code minimum size of water main, then they rehab the bathrooms, adding fixtures and in many cases adding additional bathrooms without giving a moments thought to the size of the main water line.

If you could post a list of all the fixtures in your house along with the estimated distance from the municipal main tap point to the furthest fixture in the house I would be glad to work out the math to see if your lines are sized correctly but in almost all cases when people have the type of pressure problems you are reporting, the problem is improperly sized lines and a boost pump will not solve the problem.

[jnaas2]

It could also be an old main thats full of rust, or like the last house I went to that they had installed a new 1 inch main and there still was a low water pressure problem, when I asked the homeowner a stupid question on the whole house filter if it had been replaced, He said it was new. After checking the whole house water lines for valves that might be closed I asked him if I could remove the filter just for the fun of it and he informed me it was a waste of time but go ahead.You know the water pressure was great after removing that new water filter, so sometimes it can be something simple, so try them first before you jump feet first into the big money

[Redwood]

What kind of pressure do your neighbors have?
Do they have similar problems?
Is there an old gatevalve on your service that does not seem to work...
The handle just spins...
I would consider getting a pro to check out where the restriction is.

[Gary Slusser]

You need more water, not more pressure and you can't get more water to a booster pump unless you store water from the 'city' and then boost it.

You have a restriction somewhere and the condition of the service line to the house is the best place to look first. Of course that is after you rule out a busted or partially closed valve or a water filter or softener isn't causing the reduced flow/volume of water.

[JRH]

Reply to LazyPup

I did some measurements on my water pressure over the weekend and found the following. I have 4 outside faucets which are on 1/2 inch lines off of a 3/4 inch main line. I put a gauge on 1 line and turned that line on and pressure read 45psi. I went around to the back of the house and turned on the back faucet and went around to gauge and had a reading of 25 psi. Now understand not all of the outside faucets are on the same 1/2 inch line. Each outside faucet is fed by a seperate 1/2 inch line off of the main 3/4 line.

Following is a list of my fixtures.

Master Bath-- 2 sinks, 1 jacuzzi tub, shower, and water closet with tank
Guest Bath- 1 sink, tub-shower combo, water closet with tank.
1/2 bath- 1 sink, water closet with tank
kitchen- dishwasher, double sink,
utility room- washing machine

From my water meter to the house entry point is 66 feet. Once the line enters the house it elbows over 6" then elbow up 6" with a cut off valve there and then on up another 50 inches to another elbow under the main floor and across the basement ceiling under the main floor 15" with a connector , then on across the ceiling approx 25 feet where it elbows down 3 feet then elbow into a whole house filter. After it leaves the filter it elbows over 6 inches then into a tee that branches off to a reverse osmosis filter and the other tee branch goes over to the hot water heater where it tees down into the heater and the other side of the tee goes back up to the ceiling of the basement where it becomes the main feed line.

All 90 degree turns are elbows with exception of the T at the line to the reverse osmosis and line to hot water heater. I disconnected the line at the point of house entry and had 50 psi static pressure there with 17gpm. At the elbow before the filter I had 48psi with 14 gpm. At the elbow past the heater and going up to the ceiling I had 45psi with 6 gpm.
All of the lines are 3/4 pex.

Thanks in advance for looking this over. I certainly appreciate it.
JRH

[Redwood]

So at what point are you losing the pressure/flow and what is affected?

Are you saying just the hot is low?

[JRH]

Low Pressure

Both the hot and cold are low on pressure and flow.
I am not sure where the pressure drops off but it is lousy after all the fittings around the water heater. I have removed the filter in the whole house filter and checked pressure and flow and it has no affect on gpm or psi.
Thanks for the reply
JRH

[jnaas2]

Are there any old shut off valves intsalled on the water lines

[JRH]

No, all new lines

[jnaas2]

Do you have a prv valve ? and could you take some pictures of how the lines are installed. And one other thing have you checked with the city on the water meter, some cheap ones had a inlet filter to keep junk out of them and they can become clogged

[JRH]

Water Lines

The lines are all new. There are no shut off valves between the meter and the house with the exception of the valve on the meter. I do have a shut off valve just at the point the water enters the house. This is a new home in a new sub-division. My question is if the city has a 5/8" meter outlet and I have a 3/4" pex line to the house, would I gain anything by replacing the line to the house with 1"? My thinking is that I would not. Would appreciate any comments on this.

Thanks
JRH

[wphilborne]

Figured I jump on here and ask a question about water boosters rather than start a new thread.

Can you install a pressure reducer valve after a booster pump (in addition to one before)? I have city water and the water pressure is about 35psi. A friend has a 50psi booster that I can have, but I'd really like around 60psi. I can reduce the incoming line which has a prv to 25psi. That still would result a possible 75psi of pressure.

I thought I could just install another prv after the pump and reduce it down to my desired pressure. I have seen diagrams of booster pump installs showing this setup, however I've been told by a plumber that you can't do that because it can cause cavitation and its also against code. Anyone have experience with this?