Plumbing booster pump

[lfg2007]

The toilets in a new building are not flushing correctly. It is being blamed on the size of the pump.

The booster pump which has a duty and standby pump rated at 114' head and 45 gpm each and a jockey pump rated at 114' head and 22 gpm in the basement ( elev 35’ ) has 60 psig and they are only getting 10 psig at the third floor ( elev 85”) . This is a large building and I cannot guess at the loss in the piping. This is a greywater system so there is no initial head prior to the pump.

This building has a new "green" toiulet flushing system which flushes lightly for liquid waste and heavy for solid waste depending upon if the handle is pulled up or down.

Do these numbers seem odd???

Thanks for any response.

 

[BigInch]

Don't care so much about the size of the building as the number of toilet flushes within some minutes.

Easy way to answer is go there at night, use the facilities, flush and see how they work then. If they work fine at night, you've most likely got a pump capacity or pressure problem. Then see how many you can flush at the same time before the problem comes up.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Artisi]

Please clarify;

is 114ft the design operation point for the pumps when running at full demand?

is 60psi the non operating pressure in the system (no toilets flushing)?

is the 10psi (3rd floor) the non operating pressure or the pressure available with toilets flushing?

what is the elevation of the pumps relative to the basement and 3rd floor?

Why aren't they flushing correctly?

 

[lfg2007]

Problem seems independent of the amount of toilets being used.

is 114ft the design operation point for the pumps when running at full demand? YES

is 60psi the non operating pressure in the system (no toilets flushing)? YES

is the 10psi (3rd floor) the non operating pressure or the pressure available with toilets flushing? DO not know

what is the elevation of the pumps relative to the basement and 3rd floor? Pumps are in the basement

Why aren't they flushing correctly? Manufacturer indicates it needs 30 psi at the valve to operate the toilet

It is weird that the toilets will operate better with conseqtive flushes.

 

[Artisi]

If 60 psi is the maximum pressure available and the max level is 85ft (37psi) and you need 30psi at the toilet - then you have a problem before you start, and once a toilet is flushing the pressure will drop even further as the pump run back down its curve.

That is the relevance of the basement (elev 35ft), don't understand where this fits into the discussion..

Posting a sketch of the system with levels etc might make thing a bit clearer.

 

[BigInch]

30 psi for a toilet? Is there a link to the mfgr of these things?

Don't forget to post the pump curve.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[PEDARRIN2]

BigInch 30 psi is a typical requirement for flush valve toilets in order to operate the flush valve correctly and to provide enough force for the lower flow toilets to clear the bowl.

If I understand correctly, you have 60 psig static (no flow) and your pumps operate at a boost of ~50 psi at 45 gpm for each of the first two pumps and 22 gpm for the third pump. Although you also say they are only getting 10 psi at the third floor which is about what you would get if you had no static pressure coming into the pump. The flush valves on the third floor will be ~53 feet above the pump elevation. From my rough calc's you should have ~110 psig of pressure available when you flush.

There seems to be something wrong with the numbers or how I understand what is being conveyed. Typically, water pressure to plumbing fixtures is limited to <80 psig. You seem to have more than that.

Also, was it determined that the system was flushed properly. Are all valves open all the way? Was the pump that was designed the pump that was installed?

 

[lfg2007]

Sorry for any confusion.

Two pumps 114' head 45 gpm, jockey pump 114' head 22 gpm.

50 feet from pump to 3rd floor. Guage on pump reads 60 psi.

 

[Artisi]

You still have pressure problems

50psi at the pumps when operating, pressure at the 3rd floor can only be 28psi at best without considering friction and other losses.
You need to involve the system designer - unless of course it's yourself.

 

[lfg2007]

Some more information.

The system has a stop cushion tank with a 90 gallon capacity.

If the jockey pump is not running should the stop cushion tank immediately augment the system.

 

[Artisi]

If the "stop cushion tank" is actually an air over water diaphragm tank then its role is to maintain the system pressure at a preset pressure backed up by the jacking pump. If only one or two toilets were flushed you could expect the cushion tank to service the demand and then to be jacked up again by the jacking pump. This is to overcomes the main pumps constantly hunting between start and stop.

 

[lfg2007]

Thanks for all the insight. We have found that the air pressure in the stop cushion tank was much less than designed. It will be filled tomorrow.

Several people have told me that the tie in for the stop cushion tank should be to the pump set discharge header. It currently ties in on the discharge side of the jockey pump before the Cla-Valve. I have attached a photo for refernce.

 

[steamdog]

I have seen this before with the tank piped before the PRV, this is OK, as the tank will store pressurized water at the full outlet pressure of the pump, then it will flow through the PRV valve. I would imagine that you may have some excess capacity in the system. If you have a gauge on the pump outlets before the PRV's you may find these are running at a higher pressure. Then, it will be easy to increase your outlet pressure at each PRV, and then tweak the controls to shut-off at a higher pressure.

 

[lfg2007]

I apologize ahead of time if this is an old question but I could not find it in the search.

As a continuation of my pumping problem I ask tyhe following question. When a pump is required to produce 60 psi for a grey water flushing system (2-3psi suctionside)is this pressure and flow expected to be constant when one toilet flushes?

The cushion tank has been filled but the poor flushing continues. Can gpm be tied into the problem.

 

[lfg2007]

Sorry for the added post but I am struggling with disinformation.

The manufacturer of the pump set call for the cla-vavlves to be set with 25-35gpm of flowing water. What impact would this have on the system pressure.

 

[PEDARRIN2]

A flush valve and toilet needs a certain pressure (25-30 psig) and flow rate (20-20 gpm) - for a very short time. If your system cannot supply this, then there will be problems.

What type of facility do you have?

It seems the pump and equipment are ok. It sounds like something in the piping system.

 

[ronfrend]

According to my calcs - if I convert everything to feet of head I get the following:

Shut off head point = 138' (60psi)
BEP Flow head = 114'

The flowing head at the third floor is 23' (10psi)

No flow head AT the third floor elevation (85') which is 50' above the pumps (elevation 35') = 88'
That is 138' - 50' = 88'

That leaves a head loss of 65' (or 28psi) when the water is flowing.
(88-23)

The head loss can be only friction head or velocity head as the problem with the accumulator tank has been addressed. Assuming a 2" pipe and a flow of 35gpm the velocity head is only 0.4 ft so we can ignore velocity head.

That leaves only friction head. It would appear that you need to find out why you have such a high friction head.
It could be because
1) the pipe length is too long or
2) something is obstructing the pipe diameter such as a crushed pipe or something stuck in the pipe somewhere.

I suggest you fit a pressure gauge at several locations along the pipework and find out if your pressure drop is gradual along the piping or is concentrated at one point.

Good luck




Ron Frend

http://www.predicon.net

 

[Artisi]

Ron Frend, seems to be the same conclusion I posted 6 days ago.

lfg2007 - have you discussed this with the system designer? Seems like a logical move, a least you will have the background to the initial thinking and a starting point on which to base the trouble shooting, at the moment you are snatching at straws looking for an answer and not working your way thru' it in a structure manner.