expanded plumbing in an old house
victorianchallenge
| Posted in General Discussion on
I have the challenge of re-fitting closets for additional in-room baths in an existing victorian. Town water service line is 3/4″. An engineer indicates that the service line needs to be increased to 1″ to handle the additional units. Consultants suggest using a pressurized water tank just inside to handle the needed volume and maintain pressure across the baths, with separate lines off a monitor to equalize the demand off the tank.
The consultant option seems reasonable given prior experience with well-based water systems and houses with 4-6 baths.
Does anyone have experience with this plumbing issue? pros/cons as well as methods for approaching the town planning for permits if the approach (e.g. the water reservoir) is non-standard?
Replies
My ex-plumber told me the same thing. I told him to take a hike. 3/4 should be fine unless you are running a commercial establishment. In residential, it would be exceedingly rare that all the toilets would get flushed at the same time ...
Just one man's opinion.
Roger
As long as the water pressure from the street is enough, you should not have any problems.
it seems to be volume and not pressure that they are addressing with the bigger line. if the pressure tank maintains street pressure and the monitor addresses the parallel demands on volume that could occur (the house is 6 bedrooms plus the kitchen and laundry) it would seem to address the issue..
On a related note, the plumber has recommended large indirect water heaters (4 showers in the house now that when the house is full does sometimes lose heat). The house has direct hot water from two boilers that also supply heat to 4 zones. The hot water reserve seems like a reasonable approach however, I've read conflicting specs for tankless - one suggests running the hot water into smaller supplemental hot water tank whereas the plumber says run the cold into them. In other homes that use hot water tanks, the cold has always diluted the hot and a lengthy or parallel shower has run to cold. Any experience with this?
Thank you all!
Because of the rubber bladder inside the tank. You'll have inconsistant water pressure. very similar to well fed systems.
Would the larger service line prevent this from happening?
I'm with MrSQL
Gazillions of homes have 3/4" supplies. Unless it is a boarding house and everyone has to be at work at the same place at the same time, it is unlikely the demand will be there.
Good luck
I love how everyone thinks 3/4" is just fine without knowing all the parameters.
Basic rule 100' of pipe, pressure range 40 to 60 PSI.
1/2" pipe will carry 5 fixture units.
3/4" pipe will carry 19 fixture units
1" pipe will carry 39 fixture units.
You gain or lose .433 psi for every foot of elevation change.
Fixture units are as follows.
lav 1
kitchen sink 2
dish washer 2
Washing machine 6
shower 2
bath tub 2
water closet 3
hose bibb 3
If you can't increase the size of the water service, an air bladder tank can give more flow down stream for short periods of time depending on the size of the tank.
Things to consider, an air bladder tank will NOT increase pressure.
Once the bladder has expanded to it's original size during use, it basically does nothing until the demand of water has stopped & it compresses the air bladder.
Edited 1/19/2008 3:13 pm ET by plumbbill
Plumbbill,
Okay, this is starting to give me information needed to better understand alternatives for solving the problem. Thank you and I hope you don't mind some additional questions.
If the street pressure is currently 40-50 PSI, increasing the service line would, or would not, increase pressure along with the volume of water? My understanding was that the town supplied water would not increase pressure (because it is what it is at the street) so I was not expecting that.
Are the units drawing pressure and volume and that is the limitation placed on the size of the pipe? or, is the limitation just volume of water demanded at any point in time at different points on the supply pipes? (the old first in first out scenario). If the latter, would a manifold at the tank help to even the demand for volume?
If a 1" line was on the demand side and the tank fed by the current 3/4" line from the street are there similar calculations to determine the minimum tank size (and its water reservoir) required to support up to 39 units? It would seem that the objective is to have enough of a reservoir to maintain water flow at peak demand since the flow from the street would not be able to keep up on its own.
I understand why the elevation causes a decrease in pressure. With this loss of pressure due to elevation, what is generally done to maintain pressure to second and third floor bathrooms when a well or town water cannot increase pressure?
How does the bladder respond as water from the street fills the tank to replace water that is still being demanded? Understandably, the water will be replaced at a slower rate than it is flowing out of the tank. What impact, if any, might this have on the street side flow? Can the tank maintain a different pressure than the streetside provides?
Thanks again! (any thoughts on the water heater?)
AAAAAAAAARRRRRRRRRRGGGGGGGGGGHHHHHHHHHHHHH
As I just spent the last 35 minutes typing up a reply that would confuse the best of them------ about 2 full pages
I stepped out to have a smoke & my 5 yr old just deleted my web page------------ maybe i need to quit smoking--------- I need a breather----- i'll answer later when i've calmed down-------- & no i'm not taking it out on my kid <G>
OK let's try this again ;-)
If the street pressure is currently 40-50 PSI, increasing the service line would, or would not, increase pressure along with the volume of water?
Plumbing is a lot like electricity. A larger pipe will not provide more pressure, but it will allow more flow at the existing pressure. A larger wire will not increase the voltage, but will allow more amps with less resistance.
Are the units drawing pressure and volume and that is the limitation placed on the size of the pipe?
The units draw mass (water) when that space is emptied out the supply pipe is trying to refill it as fast as the pressure provided will allow. We measure that in FPS (feet per second). We don't like to have anything over 6 FPS as that causes a premature failure to the piping system.
We size pipes on how much flow is needed for the units. We measure flow in FTU's for smaller systems, & GPM's for larger systems.
would a manifold at the tank help to even the demand for volume?
Only on the systems down stream of the manifold. A manifold is a lot like an electrical panel. You can have 10 breakers powering 10, 100 watt light bulbs, each circuit only has 100 watts, but all 10 circuits have 1,000 watts. So the lines feeding the panel have 1,000 watts loaded on it.
If a 1" line was on the demand side and the tank fed by the current 3/4" line from the street are there similar calculations to determine the minimum tank size (and its water reservoir) required to support up to 39 units? It would seem that the objective is to have enough of a reservoir to maintain water flow at peak demand since the flow from the street would not be able to keep up on its own.
You hit the nail on the head with that one.
Peak flow has no time associated with it. When we size for peak flow that is to be able to keep up with that demand 24/7. A pressure tank can't produce water, but it can keep up with peak flow for a short period of time.
Sizing a tank for your application is a bit tricky, cause it does not meet any code. But it is not impossible.
If you figure 2 GPM's for every FTU on your system, you take the tank equivalent size, & your service if in good shape will provide 20 gpm make up, I'll give an example.
Service is 20 gpmTank is 40 gallon equivalent.Demand is 60 GPM
Under a max load your tank will empty in about 3 minutes, but could be shorter or longer depending on what type of fixture unit. Water closet is 3, & a hose bibb is 3, watering your lawn puts a bigger draw on the system than flushing the toilet does.
I understand why the elevation causes a decrease in pressure. With this loss of pressure due to elevation, what is generally done to maintain pressure to second and third floor bathrooms when a well or town water cannot increase pressure?
Generally nothing. On my highrise condos we operate 5 story pressure zones that will have about 70 to 75 psi at the bottom & 40 to 45 psi at the top. If the water coming is does not have enough pressure, we install booster pumps with a pressure tank.
How does the bladder respond as water from the street fills the tank to replace water that is still being demanded? Understandably, the water will be replaced at a slower rate than it is flowing out of the tank. What impact, if any, might this have on the street side flow? Can the tank maintain a different pressure than the streetside provides?
As noted above, the tank will be refilled with a slightly lower flow than the service can proved as it goes through a check valve which cause a restriction.
Upstream of the tank while refilling will effect that system just like anything else that is demanding water.
The tank does not have a "different" pressure that the street side, but when units are calling for water it has the bladder to help push out the water, the city has the pressure, but smaller pipes restrict the flow creating a cavity which is measured by "pressure drop".
This is way shorter than the first reply I had typed up, and I kept the terms simplified.
Hope this helps.
Plumbbill,
This does help quite a bit. A key question - in your opinion, what is the best way to demonstrate to the town that this alternative is viable versus increasing the service line? Is there anything else that I should consider as I work with my plumber to put this together?
Thank you again.
If you can get a PE to sign off on a tank verses an increased line size then you will have no problem.
I deal with some of the most restrictive codes in the country, & that would satisfy the powers that be.
Selling it to the city, might be tricky without a PE, but might still be able to be done.
Talk to your plumber, if he has experience in the area he should know what has worked & what has not.
The FTU's I posted earlier are from the UPC, if your area goes by the IRC, then you might have a better shot for those codes are not as stringent.
It depends on the available pressure from the city side but 3/4" is plenty adequate for almost any residential application.
As an example, the lawn sprinkler system at my parents house in Los Angeles has two zones, one of which has between eighteen and twenty sprinkler heads, putting out about four gallons/minute each. That system runs on unregulated street pressure through 3/4" PVC pipes with 1/2" risers.
I installed that system so I'm real well aquainted with it. So, with reasonable street pressure, you could have fifteen or more toilets refilling at the same time on 3/4" pipe without a problem.
The next question is; what's the street pressure supposed to be and is it being maintained? It shouldn't fall to the homeowner to provide extra equipment to do what she/he's paying the water company to do.
Edit: I didn't read the entire thread before adding these comments so just take 'em for what they're worth on the personal experience level.
Edited 1/21/2008 1:16 pm by Hudson Valley Carpenter