I've read some previous threads concerning this topic but still can't get my problem fixed. I have a Doheny's 1.5 hp pump hooked up to a hayward sand filter. When the multiport valve is set to filter the return pressure is very low, but if it is switched over to recirculate then the pressure is fine. I have tried backwashing the filter and priming the pump again, but all was to no avail. Has anybody else had this experience.
Low Pressure in Return when set to Filter
- Thread starter rdockery_3
- Start date
Sounds like the sand is hardened into a brick. Have you ever used any clarifiers or flocculents? I'd try Deep Cleaning a Sand Filter to break up the clods.
I assume you mean there is very little circulation in the filter mode (filter psi would be high), right?
The sand is actually only a year old, it was just replaced last year and no chemicals except for chlorine have been used in it. Would it have had time to harden in a year?
I think it would be good to open up the filter and inspect the sand:Deep Cleaning your Sand Filter
That would rule out the sand itself.
That would rule out the sand itself.
I think it is definitely something to do with the sand because I backwashed it again today. The return line had very good pressure after backwashing, but after a few hours the pressure has dropped off again. Looks like its going to need a deep cleaning.
After you run for a while does the psi get higher or lower? If the pressure "dropped off" then the psi would be lower
Water is crystal clear now but it wasn't a week ago. We had an algae bloom that I'm just now getting under control.
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Pressure is higher but flow out of the return is lower. I wasn't thinking when I said the pressure dropped off, I just meant the flow did.
I just backwashed it until the water coming out of the waste was clear. Probably around 3 minutes and then rinsed for 1 minute.
How did you "get control of the algae"? Are you following the SLAM process? Passing the OCLT?
I used the SLAM process. I shocked it with bleach and then continued to keep chlorine at shock levels until water was clear. It's actually still at shock level but I think I'm going to let it come back down now because the water looks very good.
I'll probably do the OCLT tonight.
The filter is still just filtering out dead algae. Keep backwashing when pressure rises 20-25%.
Letting the pressure rise makes the filter a better filter filtering out smaller particles. The dirt accumulated helps the filtering process.
So the accumulating dirt is kind of a poor mans DE ? How high should you let the pressure rise ? The same 20 - 25 % ?