New Heater Installed, Water Pump not circulating anymore at low speeds

[whatdidigetmyselfinto]

We have recently had a gas heater installed. Pentair model.
I know for heater to be able to heat the water, you need to have the pump running faster. But I didn't expect it to affect the operation of the water pump in any other way in normal operation when not heating.

I have noticed the following :
- we have more bubble coming out of the jets when pump starts running (and for a longer time)
- I have just now realized that at 1250 rpm, there is NO water circulation. Looking into the pump, no water is coming in. I had to increase it to 2000 to get water flow.

Are these expected side effects of adding a gas heater?
Does it matter how the pipes were run (height/ length/etc?)

Thanks

 

[JamesW]

Is the in/out correct?

Do you have a picture of the system?

 

[whatdidigetmyselfinto]

I should add one more observation.

even at 2000 rpm, one of the jets (even though I don't know how things were plumbed, it is the farthest from the pump) has no water coming out...
increased to max 3250 and now there is water in all the returns.

 

[whatdidigetmyselfinto]

pictures attaced.

In/Out correct.

 

[JamesW]

Check the salt cell for scale or debris.

Backwash the filter.

What is the filter pressure on various speeds?

Do you only have a single 1.5" suction?

 

[whatdidigetmyselfinto]

salt cell was clean when i reconnected in spring. filter backwashed a week ago and not much action since then, but I can backwash for a longer time.
I will get measurements at different speeds.
Yes there seems to be a single suction, one line to pump and also one skimmer in the pool.

 

[JamesW]

Check the cell again.

What is the model number of the pump?

Also, the pump lid looks like it might be on backwards.

 

[whatdidigetmyselfinto]

Interesting that you are focusing on the salt cell.
Why I say this is because we have been having white stream out of the returns and we have always attributed that to water chemistry. It could very well be dissolving scale. we see that white stream only when the salt cell is activated.
It would be very interesting to see if the salt cell has scale/debris already in a month of use.
What is different now (compared to last year) is that salt cell was in a vertical setup and now it is horizontal, leaving a lot more chance to residue to settle.

Today pool is going to be in active use, but I will check all you have mentioned @JamesW .... Thanks for the tips.

 

[whatdidigetmyselfinto]

@JamesW :

Pump is Hayward Ecostar variable speed Pump : most likely SP3400VSP.
And I read 23 PSI @ 2500 rpm.

On and Off I see bubbles coming out. Which wasn't the case before.
Is there a leak somewhere causing drop in the ability of the pump to circulate water?

 

[JamesW]

23 psi is about 53 feet of head, which is about the limit for the pump on that speed.

Your plumbing isn't really big enough to support more than about 38 gpm efficiently.

You shouldn't need more than about 40 gpm. So, you should be ok as long as there's no excessive restriction.

There's excessive restriction somewhere. Maybe the heater, filter or cell. Check the cell for debris.

Suction should not exceed 6 ft/sec and return should not exceed 8 ft/sec.

• Size.......6 ft/sec......8 ft/sec.
• 1.5"...........38...............51 gpm
• 2"..............63...............84 gpm
• 2.5............90.............119 gpm
• 3.0".........138.............184 gpm

 

[whatdidigetmyselfinto]

I checked the salt cell. clean no debris, still, rinsed it thoroughly with a jet spray.
Backwashed again. clear water coming out.

Still reading 23-24 psi at 2500rpm.

BTW, when pump is turned off, my pressure gauge reads 10. is that normal? flawed gauge? (even though replaced last year)
Could it be the sand filter - end of life?

But why all of a sudden change in behaviour (compared to last year) - only difference is the heater addition and as a result, more 90 degree elbows along the way... not sure how much of an impact that would have.

 

[JamesW]

You need a new pressure gauge. Replace that and see what the pressure is.

 

[whatdidigetmyselfinto]

so I gather it should read zero, when no water flow (pressure gauge is on the sand filter)

 

[JamesW]

Correct, it should be zero when the pump is off.

 

[borjis]

The glycerin guage on tftestkits is a really good one at a fair price. I've had mine 5 years so far.

 

[whatdidigetmyselfinto]

@borjis Thx. I ended up getting a glycerin filled unit for triple the price of a cheapo. Much sturdy feel.

@JamesW Now I read around 13 at 2500 rpm. and max 24 when priming (3450 rpm).
Based on these, I think paths are clear, there is no obstruction.

In the afternoon i plan to go out and check for water flow from the returns at various rpms.

What I had noticed at the time though was that the water level in the pump (where you have the filter with the clear lid) was too low and i think therefore no water was getting sucked in. not sure why the water level fell like that because when it primes the system, that section is full to the top of the lid.

 

[JamesW]

Maybe a suction restriction. A single 1.5" line is not a good choice for an inground pool.

Maybe get a vacuum gauge and check the suction vacuum pressure.

 

[whatdidigetmyselfinto]

I believe the original installation (this is a rather old pool) had a drain suction line as well and that was capped off when the new liner was put in place a few years ago. I am told , according to new code, you cannot have a drain anymore. As a result, we have a 2nd suction line that is currently disabled.... and you can see that in the pictures (a line that is capped off)