Water Escaping Pool at ALARMING Rate

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T

Tanagra

0
Sep 21, 2016
3
Shelby Township, Michigan
Good Evening Everyone,

I bought and JUST moved into a 1997 home two weeks ago with an inground gunite pool with plaster. The previous owners moved up north two years ago and only came back to enjoy the home and pool in the summer months, although it seemed obvious by its condition that the pool was maintained at least weekly by somebody during the summer months...

Long story short - here are the details of the pool...

Installed 2002
25k gallons
Two pumps (one for circulation on a timer @ about 8 hours/day and one for the 'pool sweep' which just seems to add power to a return jet so I can hook up a little creeper)
Heater (gas)
Pool Slide with water valve
Pool light (500w bulb Ameri-light (or something) by Pentair)) (I just replaced this entire assembly and GFI because old light had water in it - NOT a fun job because conduit was super tight)
In-line puck chlorinator (was slightly leaking so shut it off and am adding liquid chlorine until next spring when I will replace with SWG)
Cartridge filter Pentair CCP420 (just replaced all four elements until next spring when I will move to SAND filter)

I am new to the forum and have learned a lot about pools in the last two weeks (I knew NOTHING before moving in).


So here's my story -


There was NO chlorine in the pool the day I moved in although it was blue and sort of cloudy...

Took water to store every other day to adjust alkalinity (was low), Ph (was high) and chlorine (was none).

I shocked once, added some algicide and have been adding liquid chlorine religiously to get water clear - since cleaning out ALL the algae from the niche left quite a green mess the next day. Also, have had pump running 24/7 until I get the water chemistry under control and been cleaning the filter when PSI levels rise.

Got chemistry just right and water temp up pretty high (into the 90s) and was looking forward to spoiling ourselves a little and enjoying our last week or two of warmish Michigan weather in our new pool and house. (Scheduled a close for October 20th since that is when the mesh safety cover will be installed the same day).

Water is perfectly clear and back to a beautiful blue and looks better than I had ever seen it - never has leaked a DROP (aside from natural evaporation) since moving in.


Went to work Tuesday - everything was fine.

Got home 10 hours later - water level was 8" BELOW the skimmers

Shut off ALL electricity and closed valves to main drain and skimmers at the pump

Woke up (8 hours later) - water level continues to drop - now below return jets.

Went to work Wednesday - water level still dropping - at top of light fixture.

Before leaving for work, used dye test around light fixture thinking I damaged the conduit. No dice - water doesn't flow anywhere near the light fixture.

Put foot at main drain (water only comes to my chest in deep end which is only 7'), water is escaping the drain at an ALARMING rate.

Put plastic bag on drain and it sucked it right into place, but did not completely stop flow.

About to head home from work now - am told water level is below the light fixture but draining more slowly due to my plastic bag efforts.


I understand that the pump is probably toast (least of my problems). Pump will turn on but not sure it survived since it probably ran dry for potentially 4-6 hours. It sounded ok but without water in it I cannot tell if it is 'normal' or not.


Called several people today - many talked of digging up ground and major construction into the tens of thousands of dollars, but I had one guy call and say 'Sounds like you have a hydrostatic valve in the main drain that somehow stuck or blew open - I'll be by tomorrow to replace it'.

Does this sound familiar to anyone? I understand that the valve is designed to let ground water INTO the pool to keep it from floating, but can they just up and quit in an instant and allow ALL of the water in your pool to drain in less than 72 hours?!?

Thanks for any help!
 
Hello and welcome to TFP from a fellow pool peep in the Mitten ;) I don't have a lot to offer on this one, but did wan to welcome you to the forum.

While I'm not familiar personally with anyone this has happened to, the last guy's explanation seems plausible to me so I'd be inclined to go with him. A related possibility is that sometimes pressure from groundwater can force valve open and gravel can get stuck in it when ground water recedes, as I understand it, thus leaving valve ajar slightly. So the valve might also be fine and its a fluke occurrence.

I will send you the mojo that its a simple fix either way ;)
 
If you can swim down to the main drain (or perhaps reach down to it) you should be able to remove the drain covers and inspect the valve to see if it's popped open. It would be fairly easy to see if something is stuck open.
 
It does sound like the hydrostatic relief valve (hydrostat). If there was excessive suction in the main drain, the valve top can get pulled up. The hydrostat is basically just a check valve that opens whenever there is more pressure outside the pool than inside. This normally happens when the pool is drained and the ground water is high.

However, it can also happen if there is a lot of suction in the main drain pot. Normally, the valve just snaps closed when the suction is removed, but it can stick open and cause a leak.

If the skimmers got clogged with leaves and the main drain also got clogged, it's quite possible for the hydrostat top to get pulled up. Even vacuuming over the main drain grate can pull the valve top up.

Google pool hydrostatic relief valve to see pictures of what they look like.
 
Just woke up and water level continues to fall. Shallow end is dry (so is basement - fingers crossed) but deep end at drain still is not reachable without submerging my face.

Pool 'repair guy?' coming by this afternoon to see what's what and replace hydrostatic valve if he determines that is the issue.

More info soon!
 
Confirmed!

Pool had a hydrostat at the bottom of the main drain that had failed. when pulled out, it has a degraded rubber seal and (more importantly) a rusty spring AND was barely screwed into the drain.
Was easily replaced and has positively sealed the drain (at least with dye test).

Filling the pool now to fill it back up - I will let you know in 4 days when it is full whether or not it holds...

In the meantime, should I fill pool up and add new chemicals after it is full and I have a pump running, or add 'certain' chemicals now while it is filling for the next several days?

Also, for 25k gallons, is there a simple chart on what chemicals and how much to add when filling a pool for the first time using city water?

Thanks again - SO HAPPY!
 
Tanagra said:
Confirmed!

Pool had a hydrostat at the bottom of the main drain that had failed. when pulled out, it has a degraded rubber seal and (more importantly) a rusty spring AND was barely screwed into the drain.
Was easily replaced and has positively sealed the drain (at least with dye test).

Filling the pool now to fill it back up - I will let you know in 4 days when it is full whether or not it holds...

In the meantime, should I fill pool up and add new chemicals after it is full and I have a pump running, or add 'certain' chemicals now while it is filling for the next several days?

Also, for 25k gallons, is there a simple chart on what chemicals and how much to add when filling a pool for the first time using city water?

Thanks again - SO HAPPY!
Click to expand...

http://www.troublefreepool.com/calc.html
 
If you have a blue chlorine puck floater, I would add some tabs to it and let it float in the deep end while filling. Just check pH and FC while filling; the rest can be balanced when the pool is finished filling.

Do you have a municipal water quality report? Do you normally have any problems with iron staining?

Look in Pool School, TFP publishes recommended levels there for all pool types. One uses Pool Math to figure out chemical additions.

What test kit do you have? You should also purchase one of the high quality professional test kits we recommend.
 
Typically, the hydrostat won’t completely fail that fast unless disturbed. If it was just an old seal, the leak would usually start slowly and increase over time.

Ground water can get high enough to push the hydrostat open, but in that case the pool would not drain so fast or so low. The pool water would equalize with the ground water and stop falling.

I think that the most likely cause of the failure was excessive suction in the main drain pot pulling the valve open (technically, suction cannot “pull”, it’s just a lower absolute pressure in the MD pot than under it). Because the valve was old, it did not close after the suction was reduced.

Excessive suction in the main drain pot can be due to using only the main drain and the drain cover getting clogged or using skimmers and main drain and they both get clogged or a vacuum going directly over the main drain.

To avoid a repeat, you should be careful not to create excessive suction in the main drain pot.

Make sure that the skimmers are open and clean at all times and don’t vacuum over the main drain.
 

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