Upsize Pump And/Or Piping?

[mas985]

Let me clarify a few things.

First, there is no limit to flow rate in pipe. The 8 ft/sec is a recommendation.

Second, the head loss in the plumbing is dependent on the flow rate. So on low speed, the head loss is about 1/4 of high speed.

Third, the suction side should have very low head loss since there are three pipes.

I can calculate the approximate head loss in your plumbing but I need a little more information.

What is the approximate length of your suction runs?

For the return to the pool, how many return eyeballs are in the pool and what are their sizes (e.g. 1", 3/4")?

How many 90s do you have in the heat pump install and overall on the pad equipment?

What other fittings do you have on the pad?

With this information, I can determine what the filter pressure should be given your setup and we can see if there might be an issue.

[ChuckDavis]

Suction Side:

Skimmer1 through and including mainfold - estimated 84 ft., 2x45's, 4x90's
Skimmer2 through and including manifold - estimated 36 ft., 2x45's, 4x90's
Main Drain through and including manifold - estimated 45 ft. (including pool depth), 2x45's, 2x90's
Manifold to pump - 2x90's

Pressure Side:

Pump to filter - 1x90
Filter - Tagelus TA-60, 24", zeolite media
Filter through and including heat pump bypass - 4x90's
Bypass to heat pump through and including bypass - 3x90's, 4x45's, approximately 30 ft. to heat pump and back
Bypass to (but not including) manifold - 1x90, Jandy check valve, unused Nature2 cartridge holder
Manifold to returns - Single 1.5 inch pipe, 4x90's, probably one 90 underground to split between 2 returns
Manifold to water feature - at least 5x90's

All piping is 1.5 inch
All valves are 2 inch valves with reducing couplers

Returns:

I am using Heat Snorkels (www.heatsnorkel.com). They each have a 1 inch side jet and a 3/4 inch eyeball. I removed one of the Heat Snorkels and there was no change in backpressure.

Backpressure Readings - High Speed (See notes below):

Filter on Filter, heat pump in circuit - 23 lbs
Filter on Filter, heat pump bypassed - 20 lbs
Filter on Bypass, heat pump in circuit - 22.5 lbs
Filter on Bypass, heat pump bypassed - 17.0-17.5 lbs

Backpressure Readings, Low Speed:

Filter on Filter, heat pump in circuit - 5.5 lbs
Filter on Filter, heat pump bypassed - 4.5 lbs
Filter on Bypass, heat pump in circuit - 5.5 lbs
Filter on Bypass, heat pump bypassed - 3.5 lbs

All backpressure readings are with water feature turned off.

All backpressure readings were double-checked. The 2.5-3.0 lb difference between Filter and Filter Bypass with the heat pump bypassed is notably different than the 0.5 lb difference between Filter and Filter Bypass with the heat pump in the circuit. I don't know if this could represent reaching (or exceeding) the top end of the performance capability of the pump and/or the zeolite filter media having possibly been clogged by the 2-part "floc" product that may have reacted inside the filter due to incorrect instructions from the manufacturer.

[ChuckDavis]

Hi Mark,

Have you had a chance to calculate the head on the suction side of my system?

On the pressure side, I'm thinking that I should add 2-3 lbs to the current top end of 23 lbs when back-calculating the head. As noted above it seems like the extended run to the heat pump might have exceeded the top end performance of the existing pump.

One of the online pool supply outfits recommended a 1.5 hp one-speed Pentair Energy Efficient Whisperflo pump or a variable speed pump and also changing all the above-ground piping to 2 inch. What is your opinion of these recommendations? Looking at the performance curves for a Whisperflo, and using 75 ft. of head and 50-60 gpm it looks like a 3/4 or 1 hp unit would work, but I definitely don't want to end up undersized again.

Thanks again.

[mas985]

Sorry, I must have missed your post.

With heater, I would expect about 15 PSI and with heater bypassed, I would expect 11 PSI so there is a large dependency somewhere. I am not sure where it could be. With the pressure differentials you are measuring it doesn't seem like it would be the heater or filter. Removing those does not change the pressure much. But this is probably the cause of all your problems.

Also, the 1.5 HP Whisperflo is going to be a much bigger pump than you have now so I would not recommend that.

[ChuckDavis]

Does 15-16 lbs of backpressure with the filter on either Backwash or Rinse tell you anything? Do those readings somewhat correspond with your projected pressures? (See below, also.)

All the above ground piping was replaced last year as part of a complete refurb. (Piping size was kept at 1.5 inches.) The backpressure didn't change much from before the refurb.

What I have downstream from the heater bypass is a Nature2 cartridge holder (G Series, part of original system, currently empty but used previously), a Jandy check valve (2 years old) and a Rainbow chlorinator (part of original system). There is a 1.5 inch manifold with one 1.5 inch branch to the pool returns and a 1.5 inch branch to a water feature. Underground piping is, of course, a mystery.

The Jandy check valve has unions, so I removed it and left the pipe open at that point. With the heater bypassed I got 13 lbs of backpressure and with the heater in circuit I got 20 lbs.

I then reconnected the upstream side of the check valve, but left the downstream side open. With the heater bypassed I got 17 lbs. of backpressure and with the heater in circuit I got 23 lbs.

I appears that the check valve is contributing 3-4 lbs of backpressure.

Visual inspection and manual operation of the check valve showed apparently normal operation, although the spring-loaded flapper does seem fairly strong.

According to the Jandy spec sheet, the check valve is supposed to cause no more than 0.5 lbs of pressure drop (1 ft of head) up to 50 gpm and no more than 1.0 lbs of pressure drop (2 ft. of head) up to around 90 gpm.

With the check valve fully reinstalled, I recorded pressures with one or both of the 1.5 inch pool return and water feature lines turned on. Normally I have the water feature valve partially open.

Here is the various data that I have, sorted by backpressure:

Through filter, Nature2 (empty), open pipe - 13 lbs ****
Through filter, backwash - 15-16 lbs
To filter, rinse - 15-16 lbs
Through filter, Nature2, check valve, open pipe - 17 lbs ****
Bypass filter, through Nature2, check valve, chlorinator, pool return (full) + water feature (partial) - 17-17.5 lbs
Through filter, Nature2, check valve, chlorinator, pool return (full) + water feature (full) - 18 lbs
Through filter, Nature2, check valve, chlorinator, pool return (full) - 20 lbs
Through filter, Nature2, check valve, chlorinator, water feature (full) - 20 lbs
Through filter, heater, Nature2, open pipe - 20 lbs ****
Bypass filter, through heater, Nature2, check valve, chlorinator, pool return (full) + water feature (partial) - 22.5 lbs
Through filter, heater, Nature 2, check valve, open pipe - 23 lbs ****
Through filter, heater, Nature2, check valve, chlorinator, pool return (full) + water feature (partial) - 23 lbs <normal operation>

The check valve would appear to be a problem. Are there any more smoking (or bubbling) guns hidden in all this data?

If replacing the check valve doesn't allow the chlorinator and water feature to (again) function with the 1.5 hp Super Pump on low speed, do you think that there would be a benefit from changing the above ground piping to 2 inch? (The chlorinator was just barely working at low speed.) Would the overall performance of the system improve? Would the pump run more efficiently? The three 1.5 inch suction lines could be put into a 2 inch manifold. The 1.5 inch pool return and 1.5 inch water feature line could come off a 2 inch manifold.

Thanks again.

[mas985]

In backwash mode, I would expect about 5 PSI, not 15 PSI. But I don't know what you have on your backwash plumbing either.

But in normal mode, you get 23 PSI, I would expect 15 PSI and without the heater you get 20 PSI and I get 11 PSI.

There seems to be a 8-10 PSI delta.

Does your pressure gauge go to zero when the pump shuts off?

If so, this tells me that perhaps there might be an issue with the backwash valve.

[ChuckDavis]

I think we are at the endgame here.

First, the answers to your questions. The backwash plumbing is one 90 degree elblow and 10 ft. of 1.5 inch flex. The pressure gauge does go to zero when the pump shuts off (and was replaced, see below).

The most recent diagnostics and changes:

I completely replaced the (Tagelus) multiport valve. (I disassembled the valve, checking for blockage. There wasn't any blockage, but there were small rocks (!) embedded in the (non-replaceable) spider gasket. It was cheaper to replace the whole valve than replace just the diverter.)

I installed the new multiport valve first with the old pressure gauge and then with a new pressure gauge. There were only minor differences in pressure readings between the old and new multiport valve and the old and new pressure gauge.

I temporarily removed the flapper from the Jandy check valve, but there was no change in backpressure.

Reminders: All piping is 1.5 inch. All valves are 2 inch valves with reducing couplers. Pump is a 2-speed, 1.5 hp Hayward Super Pump. Problem is that at low speed, with the heat pump in circuit, there is not enough pressure/head to operate the water feature or the chlorinator. The water feature and chlorinator will function at low speed with the heat pump on bypass. The water feature and chlorinator work fine with the pump on high speed and the heat pump in circuit.

Summary of backpressure readings:

To filter, to waste - 8-9 lbs.
To filter, to rinse - 14-15 lbs.
Through filter, to backwash - 15-16 lbs.
Through filter, Nature2 (empty), check valve, chlorinator, pool returns (full) + water feature (full) - 18 lbs.
Through filter, heat pump (incl. 60 ft. of pipe out and back), Nature2 (empty), check valve, chlorinator, pool returns (full) + water feature (partial) - 23-24 lbs.

There doesn't appear to be anything "wrong" with any particular component of our system. The addition of the heat pump and extra piping made the performance of the system marginal last year and, for unknown reasons, sub-marginal this year.

I believe I have three options:

Status Quo - I rewired the (mechanical) controller so that the timer turns the high speed pump on and off. There is no upfit cost, but there is probably extra cost for electricity. I could run the calculations and see if I could operate the pump for less than the current 12 hours a day.

Replace all above ground piping with 2 inch pipe. Benefit would be somewhat reduced since the underground return to the pool is a single 1.5 inch pipe and the underground water feature line is a 1.5 inch pipe whose valve is only partially opened.

Replace the Hayward Super Pump with a new pump, probably variable speed/flow or high-efficiency. Most of these new pumps require 2 inch piping. I could upfit the piping to 2 inches and then, if still necessary, replace the pump now or later.

Do you have any other options to suggest? What would be your recommendation or ranking among the options?

Thanks again.