Pressure question, and when do you replace sand?

I have a Hayward system, large pump, older IG pool with new vinyl liner. This is our third summer in this house. I opened late this year and had to fight a lot of algae, hence a lot of backwashing. Early on, my pressure gauge was reading normal, maybe a little low compared to the last two years (replaced the pressure gauge last summer). Now it is hardly showing any pressure at all! At first I thought it was just the gauge gone bad, which it could be, but my returns are not putting out as hard as they used to, so something isn't right even if the gauge is bad. My vac still works pretty well, though. I thought I had read on here once that low pressure might result from loss of sand in the filter - and that sand needed to be replaced every so often. I don't know if it ever has been. I don't really trust the pool place folks enough to call them out to look. Can someone advise me on this, and tell me HOW to change the sand? Thanks!

Housemom,

I cannot advise you on when to replace sand in a sand filter since I do not own one but there are plenty of other threads that have covered this topic before. Unless you see a lot of sand in the pool or in your backwash, you probably have not lost much of it.

However, there could be other reasons why your pressure is low on the filter. This usually means that the suction is high on the other end of the pump. Things to look for are valves in the wrong setting, skimmer flaps shut off, pump basket full/blocked, or even some blockage in the suction lines.

Also, what kind of drop in pressure are you taking about? From what to what in PSI?

If the pressure is low and flow is low, you usually have a water intake problem. This would be between the pump intake and the pool. High pressure and low flow usually indicates a problem between the pump outlet and the pool.

Check for dirty skimmer or pump baskets, closed valves, leaves or debris covering the drain, leaking skimmer basket lid etc.. Does the skimmer basket fill completely with water with no bubble?

Changing sand is an absolute *&$#%.

I have a DE filter now, but vividly remember the sand filter days.

Our sand filter took 150# of sand. Due to pool store ineptness, I was convinced I had bad sand two years in a row, necessitating a breakdown and replacement mid season.

Only way to get to the sand was to screw the head off the filter, use a ladel or something similar to dig the sand out. I'd reach a point where I'd get frustrated and just pick the thing up and dump it into a wheelbarrow, but my back paid for it for awhile after... :(

Knowing what I know now about pool operation from info learned here, I look back on my past years of pool store supported pool ownership and want to cry at the labor and money wasted.

Have you cleaned your pump basket out? If you haven't cleaned it out since opening your pool, chances are good there's a lot of gunk in there that is blocking good water flow.

I'd check every possible source before I'd consider changing sand.

The pressure has (previously) run consistently between 15-25 psi. It now reads 7. I have a main & two skimmers. I have tried shutting off the valves, one by one - they each read about 6-7 psi on their own. But when all three are opened, it is still just 7. I know the flow is low, because when I opened this year, I was trying to turn a jammed outlet and I couldn't keep my hand over the jet. Now I can put my hand flat on the jets without much effort. The pump basket is not leaking, nor any of the valves. No visible debris, either, but like I said, it ran fine when I opened - the psi went down after a lot of vac-ing and cleaning out baskets. I was thinking maybe something is stuck, but I don't know how to check or clean it out. The pump basket does not fill completely; there is air on top. I know it used to fill with only a tiny air bubble on top. It also used to really rattle my plumbing when the pump kicked in - pool guy told me my pump was too big for the pool (Hayward super II for 20 x 40 inground). No such rattling now. It's like it just doesn't kick in all the way. THanks for your help. I have been trying to figure out this pool stuff since moving in here. Once, in a former life, I was a lifeguard, and the extent of my pool maintenance knowledge was running the vac on Mondays. Now, I am Mom to 6 pool-crazy kids (well, one is only 4 months old, so he doesn't care YET) who just want me to keep it going and spend my days watching them swim. My husband, who doesn't swim, hasn't taken an interest in pool maintenance so far. SO...your help is very much appreciated!

Any chance at all you have a 2 speed pump and it's now set on low?

I don't have a multi-speed pump, so no idea, just a stab in the dark. I would think that if the sand were bad, your pressure would go up, not down.

Hi, Housemom,

Your second post was great.....posting all those numbers and being precise really helps.

My first reaction, is air is getting into your system somewhere between the pump impellor and the skimmers. That is causing your pump not to "prime" and that will cause greatly reduced flow. Check the pump basket lid....make sure the gasket is on correctly. If that's not it, check the drain valve(s) at the bottom of the pump basket....they need to be tight.

Find the source of that air leak and I think you'll be in business. :)

Disregard changing the sand, that is definitely not your issue.

No, not a 2 speed. I thought maybe with lots of backwashing this spring, I might have lost sand, which might have lowered the pressure.

[QUOTE=housemom] - the psi went down after a lot of vac-ing and cleaning out baskets...The pump basket does not fill completely; there is air on top. I know it used to fill with only a tiny air bubble on top. It also used to really rattle my plumbing when the pump kicked in - pool guy told me my pump was too big for the pool...No such rattling now. It's like it just doesn't kick in all the way...


I would begin to wonder if the pump impeller wasn't worn/damaged/slipping.

Housemom,

Air gets into your pools circulatory system one way......a suction side leak.

Their is air in your pump basket.

You have a suction side leak.

I don't mean to harp, (well, yes, I do :) ) but you must solve how air is getting into your system to cure your issue.

I had exactly the same problem. I've spent the last two hours checking for air leaks, then it struck me. "What if the water isn't getting to the pump because of an obstruction?"

I opened the pot and felt for the passage between the pot and the impeller (with the pump off and unplugged!) sure enough it was clogged ith vegetation! It must have found its way past the basket. Cleaned it out and the jet is noe like Old Faithful!

chalk up another vote for impeller blockage. do you have a dog swimming in your pool by any chance? my golden retriever's hair - at least some of it - gets past the pump basket and gums up the impeller, which causes a very noticeable drop in pressure.

if you or someone in your house has very long fingers, there's a chance you can reach into the channel from between the area where the basket sits and the impeller. i can on my pump, and almost every time the pressure seems unusually low, i'll find some stuff gumming up the impeller.

if you can't reach in there, you may have to take the back of the pump off in order to get at the impeller.

sometimes, the sand "channels" and you lose backpressure since the water takes the path of least resistance - meaning through the channel, if you take the multiport valve off you might be able to see if there are channels - they look like cracks in rock.