Sand Filter Pressure Problems; Sand Bad in 3 MONTHS of USE?

[MikeInMo]

When I backwash my sandfilter the psi either doesn't drop or drops only 2-3psi.

New IG pool completed last August. Has a Pentair TR140 Sand Filter (like 36" diameter, 950 lbs of sand) and a 2hp Pentair pump.

At initial setup last year the pump ran at approx 10psi and it took a long time before I needed to backwash (at 22psi). When that finally happened it only dropped pressure to the 15-16psi range. Only had to backwash 2 more times that season and each time dropped down to 15-16.

I opened pool myself and at start the pressure was 16psi but upon backwashing at 22psi it only dropped to 20psi. I have backwashed many times this season but the water never seems to be that dirty, just the high psi readings.

I called Pentair since everything is still under warranty and the rep told me that my sand has gone bad and that the only thing that will fix this problem is to replace all 950 lbs of sand.

One other weird thing - the multivalve (and yes the pump is always off whenever I switch positions). It used to be that when I pushed down on the handle and held it before turning it to a new setting it would release the pressure in th pump pot. Now the pump pot stays full unless I physically remove the top.

Please help!

[Watermom]

I'm gonna let someone else help you with this problem. However, I will tell you that your "sand has not gone bad." Many of us have had the same sand for years. I think Al (Poconos) is on his 9th or 10th season with the same sand if I am remembering correctly.

[CarlD]

950 # of sand????? are you sure? I have a 20" filter and it uses 200#.

Update: I checked Pentair's web site and a 36" does take 925 # of sand--and is appropriate for a pool with between 67,000 and 101,000 gallons! The BIGGEST home pools here we see are in the 40's... Is your pool that big?

Saying that, I'll bet ANYTHING your multivalve is bad, not your sand. It's POSSIBLE the laterals in the filter have broken as well. If you don't get a release when you push down, something is definitely wrong.

So, from what I can glean sand is not likely your problem. Something else is.

[Poconos]

When you push down on the handle that opens all ports and you probably got the drainback from air coming into the waste port. Since it now does not drain down, what do you have on the waste line? If you have one of those thin drain hoses it could simply collapse under suction and block air flow into the waste port. Thus no drain down. A stupid question and one that seems unbelievable, is it the right type of sand? Sounds like this pressure issue happened over some short period of time but not immediately. Wrong sand could slowly plug the laterals which are nothing more than pipes with slits. Also hard to understand any failure mechanism in the valve that would cause this problem. I think that filter has side mounted ports and I don't know about the internal plumbing of those things. Is it possible sand somehow got into one of the wrong internal pipes and is blocking flow? Just some thoughts.
Al

[MikeInMo]

I wasn't there when the pool builder put the sand in but even with the other issues I have with them I just can't see any company putting in the wrong sand. Could be wrong but don't think that is it.

The filter is also doing a poor job of filtering now as well and the pool is starting to show it.

Your comment about the waste line might explain bleed down issue. It wasn't until they actually closed the pool last year that they finally put one of those blue rubber waste hoses on; before that I just had 3' of 2" pipe that sent water all over my pad. (The blue roll up hose connected on to that 3' pvc pipe.)

Any additional ideas?

[CarlD]

If you already know your builder cut corners, he might well have used sand-blasting sand because it's cheaper. Even at its cheapest ($5 for 5#) your filter sand costs $95. At its most expensive, it's something like $225.

It wouldn't be the first time.

[waste]

Mike, welcome to the forum!:)

Pop the top dome off (with the system off) and reach down and feel the sand, run your fingers through it - it should be nice and fluffy (wear a long sleve shirt to prevent fiberglass splinters in your forearm). You may just have a layer of 'crud' on the top of the sand, which needs to be broken up, or scooped out, if this is the case turn the multiport to rinse when you refire the pump to wash the stuff out.

What do you mean when you say "backwash" - the numbers you're giving indicate that you might not be doing it correctly - tell us what you're doing and we'll 'tweek' anything you might be doing wrong/ missing.

Again, welcome - we'll get you through this better than the pool store or Pentair! ;)

[Sumo1]

Our church pool has four TR140 sand filters. The sand hasn't been changed in at least 15 years and does a great job. However, we replace the spider gaskets in the multiports each year. They're about $15. The multiport is a Triton model SM 20-3. We've had problems with people not pushing the handle ALL the way down before moving it. This seems to wear out the spider gasket faster. Hope this helps.
Hal
P.S. Someone told me always backwash three times. Don't know if that's just for a DE filter or if it's just hogwash but it's served me well so far.

[matt4x4]

My take on this is as follows:
10 lbs innitial fresh start up pressure sounds right, filter until 22 lbs and backwash to get 15-16 lbs - also sounds right - sand has now settled into place and is compacted to provide better filtration - thus 15lbs compared to 10lbs.
turn on system this year, filter never drops below 20 lbs - my guess here is you need a new guage - that's all, everything else is working as it should IMO unless you did not drain the filter over the winter and your laterals broke.
If you're not getting sand returned into your pool, your laterals are likely ok, and your sand is likely of the proper type.
Install a new guage (only 10 bucks) and report back - this seems to be a normal part of the whole process that continually gets overlooked and is the thing that breaks most frequently. (esp. if left out over the winter - most remove the guage and store it indoors)

[MikeInMo]

Well I switched out the gauge and the new one shows my pressure at the 15-16 range, right where I expected to be. The old one was showing 20-21 as I pulled it to replace it with the new one.

The simplest answers are usually the one that end up being right...but only if I have discarded them and then headed full force down the wrong path.

[Sumo1]

[QUOTE=MikeInMo;47601]
The filter is also doing a poor job of filtering now as well and the pool is starting to show it.


Since you've figured out the gauge problem, how's the water?
Hal