Flexible PVC Pipe (solvent weld)

[Dannie Boy]

What I was referring to is the exterior of the pipe is green plastic and the inside black so there must be some kid of bonding between the two layers. I have seen it when the inside layer comes away from the outside ( even over a very small area) which can cause a restriction in the pipe inside diameter giving an area that sludge can quickly form.
As I said before it may be a stupid suggestion.

For the relatively low cost, I’d invest in a few metres of the blue rubberised pipe that’s been suggested to see if that helps.

[hin]

Agree that so much xxx response could easily drive you cray and admire your decency to reply to so many. I have flashed onto another idea and intended keep it off the public radar by not reactivating the thread but see that has been done anyway so...

Regardless whether you have biofilm, algae, or whatever. Bio means life and refers to living things so if it is bio just need to discover how this one can be killed or altered.

I have lived in humid climates where growth on roofs could be unsightly or in extreme cases cause rotting or fire hazard. Long ago before copper was so expensive, copper sheet was the preferred roof as nothing would grow on it. When it got too expensive some builders just used a copper ridge cap and that worked well too, nothing grew in the watershed below it. In my ham radio days I also noticed nothing grew below my bare cooper antenna wire that was stretched above the roof. It was not a rapid occurrence but did happen. Ships use copper bottom paint and in the past used copper sheathing. Also some IUD’s are simply a bit of copper as the copper ions kill sperm.

If you have some bare copper wire it might be interesting to file off or bend over its sharp end then shove it down the length of the hose to see what happens. A long shot as the flow rate in the hose might carry the copper ions away too fast but again maybe enuf copper ions can coat or remain in the hose or imbed into the black growth to be helpful. Results might at best be slow but if you already have some bare copper wire it is an easy experiment. But the copper ions in IUD's need to work fast, so..? I also still think tho that the blue vinyl garden hose is worth a try as some hardware stores have it in coils and will cit off your small amount.

[Ratsima]

It sounds like voodoo, but I'm willing to give it a try. I do have several lengths of copper wire just sitting around. I'll try it tomorrow.

(I have this old-fashioned belief that everyone who bothers to post deserves a reply. I don't always meet that goal, but I try.)

[Ratsima]

For the relatively low cost, I’d invest in a few metres of the blue rubberised pipe that’s been suggested to see if that helps.

I've decided to go whole hog and buy the amount I need to get from pump to fountain. That's actually just about 8 meters, but I'll get the roll of ten. Several people on the pond forum recommended this.

[hin]

Finally read your linked garden pond forum - all of it - so this is based mostly on that. Looks like similar ratio of speculation and opinion as what you can get right here.

About hose — Pond hose…? Why bother..? If a hose is suitable for people to drink from why can’t it be suitable for fish and a pond..? You had decent luck with ½” and ⅝” in the past so the problem is obviously elsewhere, why let some people tell you that is no good. I would keep the pocket jingle jangle, and folding stuff too, and buy that ⅝” blue vinyl hose. If you decide it is not a solution am sure you will be sold on it otherwise, as a better hose to replace whatever else you have so nothing lost. Plus problem solved if Cookie’s thought is it.

Yes this is the style but probably cheaper to buy locally plus have it right now. Ours is generic brand and suits us fine.
https://www.lazada.co.th/products/takar ... 02991.html

On initially sending a tag line, or what we call a “fish” thru your pipe to pull the hose or electric wire thru - a vacuum cleaner works well. Start with small string or yarn to pull bigger line thru which will pull the hose. Our shop vac can suck or blow plus is wet or dry, both abilities are helpful but a household vac is good enuf.

If you let yourself be sold on needing bigger hose. Possibly make it easier by incorporating the existing 2” PVC pipe into the run instead of passing hose thru it. Also ordinary rigid PVC pipe is cheap + easy to work with for the entire run. That flexible corrugated stuff is best for DIYers willing to settle for less due to no skill. And buy the heavier schedule pipe. I have bent it around lots of soft curves and corners by filling with sand and using a heat gun. Heat mostly the compression side, not the stretching side. Also for this kind of job I wud NEVER use pipe elbows. Use long sweep electrical conduit elbows, Much easier water flow so easier on the pump and easier to clean out the line In Thailand they are usually yellow and stocked right next to the blue PVC water pipe.

From what you say about your prob being variable with season / temperature (beyond normal bacteria incubation differences?) your housing compound possibly has similar situation to ours. Our water is sourced from a shallow well so in actuality is just surface water, so can contain biofilm, bacteria, algae, almost anything you might possibly imagine. If so, that is quite likely the initial birthplace of yr gunk. There were lots of complaints here but no solutions. But the developer was nice to us, closed our large community pool and turned it into a settling pond after which the water is pumped up into the tall gravity tank to gravitate into our water system. Even after he took away the pool to create a ‘settling pond’ the screen on the inlet side of our water meter would plug completely every 4 to 6 weeks with all sorts of stuff including tiny clams about the size of yr finger nail. A couple times clam eggs evidently went thru the meter then grew up to block water taps in our yard. Most houses here are less effected but we are at end of a street, and water line, so maybe that helps, or unhelps, us get the extra gifts. The house has its own underground concrete tank and pump so the house water is only affected after a big rain = muddy. ± once a year we empty that tank to clean it. I installed a 400 micron filter before the meter and it went black and completely stopped any water flow in less than 2 minutes. Pulled out the element, stuffed in some plastic chore girls and now drain out black water every few days and pull the chore girls for a cleaning now and then.

So, hope my biased opinions about water quality and hose can cheer you up

[Ratsima]

Thank you for all the advice and information. I was at both Home Pro and Thai Watsadu this weekend and didn't see that Takura PVC hose at either. I'll check again and order if I don't see it. Agree with you that the hose shouldn't matter much. However, the hose I'm using now is not 100% smooth inside and maybe that might allow the biofilm to adhere. At less than 500 baht the blue hose is worth a shot.

Our Moo Baan gets its water from Tessaban Korat, so it comes from Lam Takhong reservoir. We don't have algae or biofilm problems elsewhere in the house, so I think this is exclusively a pond problem.

The air temperature definitely has an effect. It's been cool, overcast and rainy the past few days. I haven't had to ream out the hose since the rain began.

Thanks again for all your thoughts. I will study them a bit more before I either give up or decide to do something.

[Dannie Boy]

Thank you for all the advice and information. I was at both Home Pro and Thai Watsadu this weekend and didn't see that Takura PVC hose at either.

You should find it in most Thai hardware stores

[Ratsima]

You should find it in most Thai hardware stores

When I cycled to the local Home Pro and Thai Watsadu on Monday I was surprised at the dearth of choices in the hose department. Each store had a small number of reels of that plastic transparent stuff and a few packages of cheap garden hose, but that's it. I pedaled home empty-handed.

[Dannie Boy]

You should find it in most Thai hardware stores

When I cycled to the local Home Pro and Thai Watsadu on Monday I was surprised at the dearth of choices in the hose department. Each store had a small number of reels of that plastic transparent stuff and a few packages of cheap garden hose, but that's it. I pedaled home empty-handed.

Well in Cha Am there are numerous places selling it - but obviously not everywhere!!

[migrant]

What is the pond forum you referred to?

[laser]

What is the pond forum you referred to?

https://www.gardenpondforum.com/threads ... ing.16803/

[migrant]

What is the pond forum you referred to?

https://www.gardenpondforum.com/threads ... ing.16803/

Thanks!

[Ratsima]

Just knowing two flow (=pump discharge) rates, for 'clean' and 'dirty' conditions would help understanding the situation. Can you do a bit of engineering, please? The measurement is simple & easy: mark say 10, 15, or 20 L water volume on some bucket/container, then measure the time (seconds) to fill that volume by the 'fountain' outlet jet.
With those data much would be revealed already, though also would be useful to know the:
- length of the hose
- static lift (elevation difference between the water surface level in the pond and the end of the hose (discharge point)
- immersion depth of the pump

Sorry for the late reply. We've had so much rain lately that the pond was overflowing so I had to wait until the surface of the pond returned to its normal level.

And, I forgot to measure the dirty flow rate. Tomorrow or so.

Clean flow rate: 5 liters in 20 seconds
Length of hose: 8 meters
Static lift: 35 cm
Immersion depth of pump: 9 cm
(intake and output are the same depth)

Measuring the length of the hose and determining the static lift were harder than I thought. The hose runs through our homegrown jungle, so running a tape measure through there was an Indian Jones adventure. And, there is not a straight shot between the fountain output and the pond surface. I stretched a string with a line level trying to avoid the ubiquitous ferns and palms. The measurements are close, but not perfect.

IMG_1960.JPG (113.34 KiB) Viewed 448 times

This is everything that came out of the house during this morning's cleaning. Nothing solid and nothing very gelatinous.

[Ratsima]

The ultimate cause of the problem is evidently biofilm growth but discussing the reasons and management options IMO can wait for the hydraulics results. It suffices to say that there's no algae problem -> using any algacide would be a mistreatment.

Final measurement.

Dirty flow rate: 5 liters in 1:43.

So, clean was five liters in 20 seconds, dirty is five liters in 103 seconds, or about five times slower.

[laser]

That's quite a drop! To make a simple model, I took various 'new condition' hose diameters, 28 C temperature, 0.25 mm abs rougness for the hoses, 1 of 90 degree bend + some other minor losess. about twice of the bend. Pump shutoff head = 3.50 m, and the QH curve is simply a straight line from that point to the 5000 l/h (83.3 l/min) point on the Q (x) axis at zero head. This type of linear QH curve is typical for similar submersible pump pumps. To save effort I used software, and got IMO reasonable figures as shown below:

Code: Select all

Diameter [inch]	Diameter [mm]	Flow l/min	Velocity m/s
1"	25.40	42.5	1.40
3/4"	19.05	24.87	1.45
***5/8"	15.88	16.60	1.40
1/2"	12.70	9.70	1.28
3/8"	9.53	4.65	1.09
	***8.00	2.94	0.97
1/4"	6.35	1.65	0.87

Thus, about 16. 6 l/min flow is predicted by the model for the 8 m long 5/8" hose with 0.35 m static lift, quite close to 15 l/min measured value. The flow is turbulent (needed for the model) though at relatively low Reynolds numbers.
The dirty stage corresponds to a clean hose with about 8 mm (internal) diameter in the same conditions. In other words, the effect of biofilm growth corresponds to about a halved 'clean' diameter.. that's quite significant.
I stop there since predicting flow conditions for visco-elastic biofilm deposits with the obtainable data only would be wild guesswork. Btw, the software is abadonware (since 2015), too bad if one licensed it then tried to use it in 2016 on a new PC having a different hard disk serial. If someone is interested im playing with it, PM and I can give a link to the setup+fix+the model files (it runs under Windows).

pondpic.png

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It can be seen that using a simplistic model could be very wrong. Like only relying on the the continuity equation, which states that the flow rate (velocity x cross sectional area) is constant along a pipe. Then halving the pipe diameter would increases the velocity 4 times, which is a way out of the measured value.

Now, hydraulics is useful to estimate discharges but says nothing abut the cause. The biofilm topic is complex, but with some simplification one can state that most algae are phototrophic microorganisms, use CO2+light, hence cannot live in dark hoses. Ergo, killing algae would not help. In contrast, many other microorganisms, such as aerobic bacteria only can use organic carbon as food (measured as BOD/COD or DOC) and oxygen to grow and typically do not need light energy.
Biofilms are ubiquitous, present in living water and difficult to get rid of. Besides, they be utilised, see, for example, trickling filter in sewage treatment and various biofilters in drinking water treatment. The jelly-like nature of the deposit (biopolymers, mainly polysaccharides) is an good indicator of aerobic bacterial origin (there are patents to produce biopolymers similar ways). Even if the stream and pond look “clear” to the eye, they have plenty of biofilms. The question that why they like the hose? The explanation is the good food supply. In stagnant water, mass (food) transport is controlled by diffusion, whereas in the hose the flow/mixing enhances the delivery and uptake of the food. Of course, increasing the water velocity increases shearing, and removes some of the film, thereby creatings a dynamic balance.

For the new pond a small hose & pump was good enough, right? But with the gradual accumulation of organics and nutrients, the increased food supply has created an issue. The solution is obvious: reduce the available food supply. Frequently removing the sediment from the pond and diluting the pond water with fresh water make it sustainable/manageable, and even can provide regular activities and exercise. But if those are becoming a pain then consider installing a small, home-made biofilter to provide a better place for slime growth. For this small system a plastic storage box or drum would suffice, adding some piping and suitable filter material (sponge, non-woven textiles, rings cut from an old hose.)