In our part of the country with a water table that doesn't typically cause any issues because it is so deep we don't use hydrostatic relief valves. Instead we plug the port in the bottom of the main drains as the pool is being filled. The other hydrostatic relief plugs not in the main drains (closer to the shallow end) also get plugged.
When the customer every has to empty their pool, we advise removing the plugs just to be on the safe side (even though our water tables are very very deep (40+ feet.)
My question is...does anybody else use plugs like this, and if so, do you put a piece of perforated pipe below the main drain where the plug is or do you rely on the stone base to allow for water flow?
tony c
Comments
I should say that if know for sure you have a severe high water table, whereas water comes up like a geyser even in the shallow end plugs, prior to draining it may not be a bad idea to hire a diver to remove those plugs as well as the deep end plugs.
Water is super powerful! Especially after this snowy winter there's quite of water in the ground form the melt down. Very saturated. Allowing that water pressure to relieve itself may prove worthy.
Anthony I am located in northern New Jersey. Yes, I experience freeze/thaw conditions. We presently have 2 empty pools we shot at the end of the year prior to the bone chilling temps in December.
One site we hit ledge stone at 2' depth and subsequentally have to hammer out the entire deep section (9' depth, 8' finished) and a good portion of the slope on an 18x36 pool. I was concerned about the ground water as it essentially had no place to "perk". The rock at the bottom of the dig even with it's cracks and fissures slowly drained water.I left the ground water plugs out and plugged the suction ports to prevent water from getting into the pipe. The water comes in very slowly enough not to really freeze solid at the bottom. Like a dripping hose spigot.
Fortunately, the best thing was for the snow to come and actually insulate and "warm" the shell. It was mightly cold before the snow came. The pool right now is nearly half full from the snow and several meltdowns. Everything looks OK.
The other site I had a concern as the soil conditions yielded clay. An expansive type soil, it does not perk very well. I have this behind the shell. Here too we leave the plugs out. Snow helped out too. That pool is OK.
I have read where others have put down straw/hay to limit it's exposure and hopefully prevent freezing. Might be a messy cleanup in the spring. Smells like a barn too-customers love that. Even tenting and running heat.
Hydraulic cement is a temporary fix. I d
Kevin,
Thanks for the detailed description. That is exactly what I was looking for! We do exactly what you suggest, but we have added some plugs in the shallow end, which I don't think we need since any water would follow the stone down to the deep end anyway.
One more question... Do you build in a freeze/thaw area? We are going back and forth as to what is the best method to use when we need to leave a concrete shell sit over the winter without finish. There are 2 schools of thought in our area:
1. leave the shell empty and keep the hydrostatic plugs open. This allows snow/melted ice to drain under the pool shell...but it keeps the hydrostic plugs open for safety.
2. fill the pool up to the steps and have the plugs closed. Since there isn't finish in the pool yet, this often is a headache since the water sometimes drains down. We place hydraulic cement around the fittings...but we still sometimes loose water...and I don't like the thought that I am not adding water to under the shell!
opinions? I have done both...haven't had a problem yet...but still am not 100% happy with either method.
I thought about using a hydrostatic valve in the winter, but I am concerned about water puddling and freezing and keeping the valve closed.
During construction on our gunite pools, we over excavate at least 1' in the deep end and add crushed 3/4" stone/gravel. This is to provide a good bed for the structure to be placed upon as well as allowing any ground water to seep through the clean stone.
We only use the hydrostatic port in the main drains. The perf pipe beneath the drain pot is not necessary if there is adequate stone. Remember the perf pipe has to go into a stone base and not the soil anyway.
If the base is very sandy upon excavation, we may use a little more stone as the sandy soil could perk up through the stone. We won't use the hydro access plugs on the floor as the plaster crews finish them off nicely and in order to open them the plaster must be chipped away. Using a standard concrete wall fitting with a flush plug would solve the problem but appear unsightly.
If we encounter water, we will control it with an electric sump pump buried in the stone or run a 2" pipe from the bottom beneath the stone to the surface and attach a standard pool pump. This is pretty much customary.
We have in the past buried the electric sumps deep in the stone bed, running until the pool was shot and even after plastering. A sacrificial necessity to control the water.
If we know ground water will continue be an issue even after construction, we will install an automatic spring loaded releif valve made by Hayward. This will allow the introduction of the ground water into the pool relieving pressure behind the vessel in the event of exessive hydrostatic pressure. It's worth it for about $25 bucks.
We built a pool about 6 years with these conditions. A week after 10 days of heavy rain, my customer noticed the pool "filling". The initial thought was a broken auto water leveler. It was actually the ground water activating the automatic valves. I can imagine the results had we had not installed these items.
I recommend changing them every few years
Lester,
Thanks. My thoughts exactly. But as usual, whenever I suggest to my plumber (or others) that I want to do something "the right way" they respond with "no one else does it like that!" I just wanted to make sure I wasn't over thinking this.