Question on Check Valve for Gravity-Fed Condensate Drain 5

[michael333]

I've designed 2 horizontal fan coil units with cooling coils above a lay-in ceiling. I've routed 1 inch condensate lines from each FCU into a common 1-1/2 inch cond line. The common 1-1/2 cond line is then routed and connected to an existing 4 inch storm drain stack rain leader (SD). I've used a "no-hub comb Y and 1/8 inch bend fitting" (in the 4 inch storm drain) to connect the new 1-1/2 inch cond line to the existing 4 inch storm drain stack. The cond drain line is sloped down into the rain leader.

Client has sent me the following issue:
They had heavy rains at the jobsite yesturday. The cond drain installed for my 2 horizon FCUs was allowing water to run back onto the floor in the room that these FCUs serve. Apparently, the existing 4 inch SD has a drainage problem with heavy rains. The mech contractor's solution is to install a check valve within each cond drain line for the installed 2 FCUs. They think this will ensure good drainage and prevent this from happening again. Here are my questions for anyone out there willing to give advice:
1) I think the check valve idea is a bandaid for the real issue. Why doesn't the client utilize their clean outs in the exist 4 inch SD? Correct?? That's the first thing I'll recommend.
2) If I have to spec a check valve (CV) for the mech contractor to install, what kind of CV do I need? Has anyone out there ran into this? Am I even allowed to install CVs in cond drain lines? These CVs need to assure good drainage with only gravity flow from the drain pans of the FCUs when installed. Is this possible for gravity-fed drain lines?

Any input/advice would be appreciated.

Mike V.

 

[MechEngNCPE]

I don't think you are allowed to install a check valve in a gravity condensate drain, if you had an internal condensate pump, that would be one thing.

This is why you are not supposed to connect directly to a drain. You need to have a 2" air gap (indirect waste) for condensate removal. Route your condensate line to the nearest floor drain and provide air gap.

 

[MechEngNCPE]

There are condensate pan pumps that lay in the pan as well, could you provide a hub drain on a plumbing stack to drop into.

 

[MintJulep]

So when it's raining and the storm drain is full and the check valve is closed where will the condensate go?

Onto the floor.

 

[MechEngNCPE]

haha I got a chuckle Mint.

 

[willard3]

Check valves take a certain pressure to operate and will back up condensate until this pressure is reached.

What is the height difference between the pan and drain?

The comment on the air gap is also correct.....you don't want storm or sewer water to back up into the drain pan. Codes require the air gap for a very good reason.

 

[michael333]

Hi willard3,
Thank you for your input.
Thanks goes out to MechEngNCPE and MintJulep as well.

The height difference between the pan and drain is 2 inches, 3 inches at the most.

I'm going to recommnend they install a condensate pump in the 1-1/2 common cond line and re-route it to the nearest floor drain or sanitary line.
I doubt I'll find a check valve to do this.

 

[ChrisConley]

On the plus side, once you have your condensate pump you can install a check valve!

 

[cry22]

Install a condensate pump ($75.00) for each FCU with check valve ($10.00)for each pump. That should solve the problem.
Connection of condensate to sanitary lines is against code in some jusrisdictions. Connections to floor drain, only if floor drain connects to storm drain for some jurisdictions.

 

[317069]

I think that it is not your problem as a HVAC design.
it is a plumbing issue.

 

[MechEngNCPE]

Some engineers like to understand more than one specific discipline. I stamp HVAC/Piping/Plumbing/Fire Protection dwg's.

 

[Ziggypump]

I'm still relatively new to the field, and as soon as I read that the condensate was attached to the storm drain, my thoughts immediately went to the problem you're experiencing. I don't know if having issues with the drain is causing the backup into the condensate line. A lot of rain means a lot of volume, and you also have the path of least resistance.

Do you have a DDC system or something to go along with the pumps? I don't like to use pumps when I don't have to because if it breaks, now you've got water problems. Maybe some way to tie an automatic shut off to the unit if the pump fails?

 

[317069]

some engineers suggested to install a pump, check valve and bla bla bla, but they didn't tell where this pump will discharge.

 

[AnotherEllis]

You can use a condensate pump with an overflow shutoff switch tied into the FC. If the pump fails for whatever reason, the fan shuts off or the chilled water valve closes.

A shut off is standard practice here in South Florida in any coil drain pan.

http://www.ellisconsultingengineers.com

 

[cry22]

317 says:
some engineers suggested to install a pump, check valve and bla bla bla, but they didn't tell where this pump will discharge.

The suggestion actually says where to discharge. i.e. depending on where you jurisdiction allows. in my area, discharge must be to the storm. Reason being that the water utility company does not want to deal with "un-metered" water to the sewage treatment plant. Imagine all Condensate in a city dumping into the sewer system, the city will need a larger treatment plant.

Some jurisdictions have a combined sewer (storm and sanitary). The answer given refers to the AHJ for these reasons. Refering to AHJ is not exactly bla bla bla.

Next time, change the tone of your posts - you come out cinical and not appreciative of the proposed solution in your post and you do not seem to grasp the big picture - if you need additonal info, just come out and ask, no need to B*** people out to get an answer. But it's oK, we are forgiving folks here.

 

[317069]

I am not B*** to get your answar
I just gave an opinion about a matter most of you treated it as a design problem where it is not.
if you read the question carefullly, you should understand that it is not an HVAC design problem
it happened after a heavy rain fall, so I suggested it is a plumbing problem but someone attaced me and said that he stamped hvac, plumbing and bla bla bla, good for him.
So, next time Mr forgiver read the problem carefully before you B*** people

 

[AnotherEllis]

Wow, such angst.

I stamp HVAC, Plumbing and Fire as well. To be a good designer you have to understand the systems you design as well as the systems your design interacts with.

I have to tell you that from a liability standpoint, if the storm drains backed up and were slow prior to you tying into them, but they did not leak into the building, nobody cares. The minute you tie into them and the water intrudes, it's your monkey.

If this turned into a claim against you or your employers insurance policy, rest assured they will fold and settle in a heartbeat. And you will be out of pocket your deductible as well as heightened premiums.

Anyway, have a happy b**** free weekend, everybody!

http://www.ellisconsultingengineers.com

 

[317069]

Cry:
Sorry I didn't mean to comment on your solution, I respect your experiance and every body's experiance, I thought someone else has suggested the pump solution, I appologize.

AnotherEllis: you are right we have to understand everything related to the job we do. and also we have to know who has to correct the problem too. and that what we are trying to do here.

For this problem, my opinion is:
The drain is connected to the rain ladder, so I guess this project has been checked by the city hall based on the applied code in the area.
Because of a heavy rain, the drain connection allowed water to go back to the space(this water is comming from the roof not from the HVAC units)
- If we install a pump and keep the drain connection as is, how the pump will work, it will suck water from the unit pan and disharge it to rain ladder, in the heavy rain case the rain ladder is already full of water, it is like we have a small pump suck water from a small tank and discharge it to full bigger tank.
- If we install a pump and change the drain line rout to let say a floor drain, I don't think we need a pump or anyother devise in this case because the problem is not a condensat water.

I think the plumber has connected the drain line in a wrong way.

also the unit manufucturer for sure has instructions regarding to the drain line installation and it should mentions if we need to install a pump or check valve or anything else.

That what I have tried to say from the first but sudennly a folke attacked me and gave me a lessons I like to have it but in such way.
I appoligize again and happy weekend for everybody and specially for you Cry22

 

[BronYrAur]

I always tie into an "open site" drain. whether it's storm or sanitary, do not tie directly into it. Always provide an air gap as MechEngNCPE suggested. If you route the 2 units into a common line, put checks after the pumps. If they are routed separately, you don't need the checks.

Not to open a new can of worms, but is this a plenum return ceiling? If so, you may have issues with the pumps you select if you want to put them in the plenum.

 

[KiwiMace]

The pumps have checks integrated. Without these the lift section will drain back into the pan and endlessly cycle the pump.