- This topic has 10 replies, 5 voices, and was last updated 23 years, 11 months ago by
TheLocalPlumber.
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MasterPlumbers
What causes water pressure to drop when you flush a toilet, can it be corrected, and how expensive is it?
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This condition happens a lot where the installing plumber doesn’t not allow for the proper sizing of the flushometer piping and also fails to use a dedicated line just for these flushometers
You can try to run a separate line (dedicated) strictly for flushometers as flushometers require around 25 PSI min and a flow rate of around 25 GPM
Picture a garden hose going full blast. Now picture this same hose with a double connection see the drop in pressure and also the volume as you splitting this in half.
A flushometer is a great device BUT unfortunately a lot of contractors try to cut corners with under sizing the supply lines to this fixture. Another problem associated with flushometers using an undersized line is the flow rate Velocity in FPS which, on copper tubing can cause erosion if left unchecked ( no more than 8 FPS is recommended)
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If this is a flushometer operated toilet, then this is your problem. When the toilet is flushed, the valve opens almost instantly, but water being rather lazy, does not start flowing immediately. Therefore the pressure in the line drops to about zero until water starts flowing, and then the pressure increases dramatically for a few milliseconds. This can cause a serious water hammer and pipe fitting fracture if the pipe is not rigidly secured. I usually install a small-trol tank in the piping near the flushometer to maintain line pressure while the water in the service line overcomes its inertia.
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I did not see anything in your post about a flushometer, so I will answer as if there is not one.
If you are taking a shower and the toilet flushes and decreases water pressure, then you could have old galvanized steel pipe delivering your water service.
The problem could be anywhere between the meter and the fixture, probably all the piping has decreased diameter and once determined to be a problem should be re-piped. Good Luck.
A test would be to install a pressure gauge at front hose bibb and flush toilet, at same time have someone watch to see if the pressure gauge drops.The Local Plumber
Tustin, California
http://www.thelocalplumber.com -
Am I correct in assuming that repiping is the only solution when you have badly corroded galvanized pipe? In other words, there is no solvent or other (safe) means to remove internal corrosion in situ? I’m in a 16-story apartment building of some age and have this flushometer problem and getting them to repipe is unlikely. I also suggested switching to tank toilets, but no go…
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OK so your in a 16 story building BUT the key is HOW HIGH is the roof tank above your fixture. All the roof tanks I have installed are designed to give about 25 PSI
(58 ft above the fixture)Roof tanks are fantastic for high rise buildings as you have plenty of reserve water for a fire stand pipe plus more than enough domestic water supply.
The only draw back with these tanks is lack of maintenance by in house staff.
These tanks depend on gravity to supply the system but these tanks by code should be cleaned out yearly and here lies the problems.
A lot of these tanks have defective covers where pigeons can get into the tank and drown and as they rot the feathers can and do plug up the supply piping for the building. ( I pulled many bird feathers out of running flushometers)
To find your actual pressure at your flushometer is simple measure the tank discharge line above roof level and then find out your fixture height from the roof.
Add these two numbers and times this by . 434 this will give you the static pressure available PLUS the actual water level inside the tank.
There are a lot of tricks we high rise plumbers do when the piping is corroded internally to rectify the low pressure/low volume problem.
The easiest way is replacing the existing flushometer with a Sloan Naval low pressure type that uses hydraulics OR replace the piston type (Sloan Gem) with a Sloan Royal or Coyne Delany flushboy or REX low pressure enlarged diaphram type.
The repiping is a last resort as it is very expensive and a mess .
I normally use a low down tank and bowl on the upper floors when a pressure problem arises.
Just think about the poor folks on the lower floors when the pressure reducing valves fail and they have a 47+ stories head of water on their flushometers / faucets KA POW 245 PSI FLUSHING pressure
Forget chemicals to remove scale or rust if indeed you have galvanized piping. There is something called water jetting that has been successful in removing scale BUT this is not a cure all. Some times back flushing can help
Here is an article you can read that may give you some insight.
In the near future I will write another article about the virtues of roof tank water supplies and the pit falls.
http://www.masterplumbers.com/plumbing/plumbviews/watersupply.html
pgarrity wrote on 26 May 2000 at 06:54 PM:
Am I correct in assuming that repiping is the only solution when you have badly corroded galvanized pipe? In other words, there is no solvent or other (safe) means to remove internal corrosion in situ? I’m in a 16-story apartment building of some age and have this flushometer problem and getting them to repipe is unlikely. I also suggested switching to tank toilets, but no go… -
Yes re-piping is your only viable alternative. In a building that is 40-50-60-years old and problems with old galvanized pipe, anything else would be just wagging the tail of the dog.
What are they waiting for?
Bill
The Local Plumber
Tustin, California
http://www.TheLocalPlumber.com -
TheLocalPlumber wrote on 27 May 2000 at 03:16 PM:
Yes re-piping is your only viable alternative. In a building that is 40-50-60-years old and problems with old galvanized pipe, anything else would be just wagging the tail of the dog.
What are they waiting for?
Bill
The Local Plumber
Tustin, California
http://www.TheLocalPlumber.comBill a lot of building are rent controlled and thus means the land lord cannot afford to repipe until the government allows the land lords to make a profit on their investment.
Imagine if you owned a building and then the government tells you how much you can charge to a renter?
The idiots in government have no idea of the actual cost of running a business or a building. Look how many buildings are in the slums THAT the Government owns DUH poor building management and lack of proper maintenance.
I still service building with Galvanized wrought iron OVER 100 years old and they are still in good shape same with Yalloy piping.
There are lots of viable options in this job long before a total re pipe is required.
Look at most big old cities in Europe and even here. How come a lot of these cities have origional piping over 150 years old still on the job? Proper PROFIT margins for the investor thats why.
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Sylvan, you are right. I still have a mindset that all of these questions are coming from America.
In California, unless the building is a slumlord building, all owners would want to look at the prospects of a copper repipe rather than subject its tenants to the misery that accompanies a 100 year old building and the problems associated with 100 year old galvanized steel piping.
It is possible to get another life out of 50-60-70- year old piping but at that point it is wagging the dogs tail. Much needed repair of old piping does not justify the expense, when at some time in the near future, because of poor water pressure,rusty water,etc., the building will need a re-pipe. So all monies spent on repair are usually repeated in a re-pipe.
Now in the country of Russia, Africa, Mexico or as you say New York the reason money is not spent is because there is none. It is not right to the tenant to have continued headaches because the landlord is postponing the inevitable.
We find that most Plumbing Contractors, or Master Plumbers that do not at least look at ending the burden of a non-ending nightmare for most tenants and owners, are not capable to do a re-pipe in a building that size, and thus wag the tail of the dog.Bill
The Local Plumber
Tustin, California
http://www.TheLocalPlumber.com -
Billy the fact of life is as follows. A lot of rent controlled building are set way below fair market value. For example one of my accounts has some person who is paying LESS that $100 per month BUT an exact same apartment on the same floor not rent controlled is rented for over $1,500 per month.
Do you honestly expect ANYONE in their right mind to invest several thousand dollars in this $100 per month apartment, as they can never recoup the investment?
Unlike California NYC doesn’t allow anyone to do plumbing (up to $500) as California actually encourages ANYONE to dabble in this field.
California also allows home builders to do a lot of the electrical and plumbing work with little or no training.
We both know how CHEAP labor is in your state and this is not the case here.
For a simple basin stoppage we get over $125 BUT I am told in your state you have folks coming riding around in cars doing this job with NO insurance or licenses for less than $40.
A repipe again is a very expensive proposition and a lot of times not necessary.
Your not taking into consideration a lot of building are classified as land marks and the historical societies frown upon plumbers destroying in laid wood/marble walls.
Living in your state where most building will most lightly tumble in the NEXT BIG ONE it is OK to figure repipe as not many Calif. cities have old structures standing.
Bill care to tell me the correct location on YOUR T&P installation on a furnance? As this is something new to me and Im always willing to learn
SylvanLMP wrote on 23 May 2000 at 02:45 AM:
What Furnace has a T&P Valve?
California SURE has some STRANGE laws. Most of the “furnaces” that I have seen have a high limit control. Where does this “furnace” get the water from to activate the T&P?
I have seen an operating controllers and even a high limit controller BUT a T&P that is AMAZING.I think I had better learn something about this profession before I make a foolish statement.
That drain is probably there per code, check with local authorities.
An existing drain is a good reason why it stays bone dry, remove it and you may have a wet surprise one day.
I am more concerned about a plastic line running from the furnace T&P valve. If this pipe were ever needed, it could pose a health and safety hazard to children playing close by. Have this pipe changed to either copper tubing or galvanized steel.
Bill
The Local Plumber
Tustin, California
http://www.thelocalplumber.coWhy did you erase your insight on this T&P issue? It is a Calif thing HUH?
[Edited by SylvanLMP on 28 May 2000] -
Sylany,
You are the only professional that can give advice on this forum?
I dont think so.You have derailed more than one qualified individual with your I am greater than thou,crap.
You find something wrong and ride it to death. Come on this is advice here, take it or leave it.
If I lived in the Bronx I would be higly amused at this form of enertainment as well, Get a life.
But no I am not going anywhere, and you will not ride me off like you have countless others. For I have seen your kind before and dealt with it. The more you have to prove the louder you get.
Bill
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